The primary factor to determine system criticality is the maximum allowable downtime (MAD), which is the maximum period of time that a system can be unavailable before causing significant damage or risk to the organization. The MAD reflects the business impact and the recovery requirements of the system, and it can be used to prioritize the systems and allocate the resources for disaster recovery planning. The other options are not as important as the MAD, and they may vary depending on the system characteristics and the recovery strategy. The recovery point objective (RPO) is the maximum amount of data loss that is acceptable for a system. The mean time to restore (MTTR) is the average time required to restore a system after a failure. The key performance indicators (KPIs) are metrics that measure the performance and effectiveness of a system. References: CISA Review Manual (Digital Version) 1, page 468-469.

The charging method for IS resources is the way that the IS function allocates its costs to the users or business units that consume its services. The charging method can affect the behavior and incentives of the users and the IS function, as well as the efficiency and effectiveness of the IS resources. Therefore, choosing an appropriate charging method is an important decision for the IS function and its stakeholders.
One of the possible charging methods is to charge specific costs that can be tied back to specific usage. This means that the IS function tracks and measures the actual consumption of each user or business unit for each IS service, and charges them accordingly. For example, if a user uses 10 GB of storage space, 5 hours of CPU time, and 100 MB of network bandwidth, the IS function will charge them based on the unit costs of these resources. This charging method has the advantage of encouraging the most efficient use of IS resources, as it provides clear and accurate feedback to the users about their consumption and costs, and motivates them to optimize their usage and avoid waste or overuse. This charging method also aligns the interests of the IS function and the users, as both parties benefit from reducing costs and improving efficiency.
The other possible charging methods are:
Total utilization to achieve full operating capacity: This means that the IS function charges a fixed amount to each user or business unit based on their proportion of the total operating capacity of the IS resources. For example, if a user or business unit has 10% of the total computing power allocated to them, they will pay 10% of the total IS costs. This charging method has the disadvantage of discouraging efficient use of IS resources, as it does not reflect the actual consumption or usage of each user or business unit, and does not provide any incentive to reduce costs or improve efficiency. This charging method also creates a mismatch between the interests of the IS function and the users, as the IS function benefits from increasing costs and capacity, while the users bear the burden of paying for them.
Residual income in excess of actual incurred costs: This means that the IS function charges a markup or profit margin on top of its actual incurred costs to each user or business unit.For example, if a user or business unit consumes $100 worth of IS resources, the IS function will charge them $120, where $20 is the residual income for the IS function. This charging method has the disadvantage of discouraging efficient use of IS resources, as it increases the costs for the users and reduces their value for money. This charging method also creates a conflict between the interests of the IS function and the users, as the IS function benefits from increasing costs and profits, while the users suffer from paying more than they should.
Allocations based on the ability to absorb charges: This means that the IS function charges different amounts to different users or business units based on their ability to pay or their profitability. For example, if a user or business unit is more profitable or has a higher budget than another user or business unit, they will pay more for the same amount of IS resources. This charging method has the disadvantage of discouraging efficient use of IS resources, as it does not reflect the actual consumption or usage of each user or business unit, and does not provide any incentive to reduce costs or improve efficiency. This charging method also creates an unfair and arbitrary distribution of costs among the users or business units, as some paymore than others for no valid reason. References: 1: Charging Methods for IT Services - IT Process Wiki 2: IT Chargeback Methods - CIO Wiki 3: IT Chargeback - Wikipedia

The only thing that can be provided by asymmetric encryption is nonrepudiation. Nonrepudiation is the ability to prove that a message or transaction was originated or authorized by a specific party. Asymmetric encryption uses a pair of keys: a public key and a private key. The public key can be shared with anyone, while the private key is kept secret by the owner. If a message is encrypted with the sender's private key, only the sender's public key can decrypt it. This proves that the message was sent by the sender and not by anyone else. This is called digital signature and it provides nonrepudiation. Asymmetric encryption can also provide information privacy by encrypting a message with the receiver's public key, so that only the receiver's private key can decrypt it. However, information privacy can also be provided by symmetric encryption, which uses a single key to encrypt and decrypt messages. References:
* CISA Review Manual (Digital Version), Chapter 5, Section 5.21
* CISA Online Review Course, Domain 3, Module 2, Lesson 12