What must be considered for custom basis formulas? There are 2 correct answers to this question.

What must be considered for custom basis formulas? There are 2 correct answers to this question.
A . The custom formula must use fields from the employee history file
B . Fields to be used in the custom formula must be defined as ffld or ifld fields
C . The basis field(Field type ffldl) must be used to define the custom formula.
D . The custom formula must use fields from the user data file

Answer: B,C