If 5^21 x 8^7 = 10^n what is the value of n?	Choose the correct answer.
A) 26 B) 24 C) 21 D) 28 E) 20

Rationale: 5 ^ 21 * ( 2 ^ 3 ) ^ 7 = 10 ^ n or 5 ^ 21 * 2 ^ 21 = 10 ^ n or 10 ^ 21 = 10 ^ n n = 21 c
Answer: C