When should a time and material $($T&M$)$ contract with a contractor been chosen vs$.$ a fixed price contract?

Group of answer choices

When only a limited amount of money can be made available to fund the project.

When cost risks for the customer should be limited but not schedule risks.

When subcontractors are being used and the customer will reimburse their invoices.

When scope includes the progressive elaboration of the scope of deliverables.