How do you satisfy this requirement?

A requirement for a hotel reservation case type states that as customers change their room selection, the total cost of the reservation updates accordingly.

How do you satisfy this requirement?
A . Configure a calculation for the total cost held.
B . Configure a validate condition for the total cost field.
C . Configure a field group list for all the room types.
D . Configure a when condition for the total cost field.

Answer: C

Explanation: https://collaborate.pega.com/question/test-process-flow