Offer and acceptance together make up 'agreement'.

Cost transparency - this requires a high trust level, as both parties open up and share information on the costs of their operations.
Open book costing is a one-way share - the seller allows the buyer to look at their actual costs.

An opportunity cost is the cost of not being able to do something else.
For example, if a firm opts to build a new factory, it may not be able to create ten new retail outlets which was another option open to it, in spending these particular funds. Or if you buy a holiday, you may not be able to buy a new television. The television is the opportunity cost of the holiday ie the benefit foregone.
The other types of cost shown are methods of classifying actual (real) costs. Opportunity costs are, in a sense, not real; they are hypothesized and therefore do not show in the balance sheet or profit and loss account of a business.

'Five-Why Analysis' or 'Why-Why Analysis' is an approach to trying to determine the cause of an event. It can be used to link to / in conjunction with an Ishikawa diagram. The principle is that one repeatedly (as often as necessary, not necessarily limited to five) asks 'why?', and eventually an un-derlying reason will emerge, which if addressed effectively, will successfully resolve the problem. This is something which can often be observed naturally in small children. 'Why, Daddy?'. 'But why, Daddy?. Etc. (Or Mummy)

These are 'model form' contracts. Industry standard templates eg NEC ('New Engineering Con-tract'); or FIDIC model form contracts. You will find some examples produced by CIPS on the CIPS website eg for IT procurements.