Korsak Corporation Is a Service Company That Measures Its Output

Korsak Corporation is a service company that measures its output by the number of customers served. The company has provided the following fixed and variable cost estimates that it uses for budgeting purposes. The planning budget for October was based on serving 23 customers, but a total of 19 customers were actually served during October.
The activity variance for total expenses for October would have been closest to:

A) $6,400 F
B) $6,400 U
C) $7,900 U
D) $7,900 F