What is true about a custom tab?

Universal containers has a custom object that has a N:M relationship with opportunityLineItem carrying price and amount information. In order to compute total amounts and total prices per Opportunity using Rollup summary fields, what field type will you use.

Which of these is not a valid report type?

Universal Containers needs to update a field on an Account when an Opportunity Stage is changed to Closed Lost. What tools can we use to accomplish this requirement? (Choose 2)

Universal Containers needs to create a roll-up summary field on a custom object that counts the number of related records on another custom object.
What type of field must exist before the roll-up summary can be created, and where should it be located?