Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[EX Q]: Problem: if price of t. v set is reduced by 20 %, then its sale increases by 80 %, find net effect on sale value
Options: a. 44, b. 45, c. 46, d. 47, e. 48
[EX A]: a

[EX Q]: Problem: ravi purchased a refrigerator and a mobile phone for rs. 15000 and rs. 8000 respectively. he sold the refrigerator at a loss of 5 percent and the mobile phone at a profit of 10 percent. overall he make a.
Options: a. 50, b. 288, c. 27, d. 200, e. 881
[EX A]: a

[EX Q]: Problem: ( ( ( 13 ! ) ^ 16 ) - ( ( 13 ! ) ^ 8 ) ) / ( ( ( 13 ! ) ^ 8 ) + ( ( 13 ! ) ^ 4 ) ) = a then what is the units digit for a / ( ( 13 ! ) ^ 4 ) =
Options: a. 7, b. 8, c. 9, d. 6, e. 5
[EX A]:
c