Cost is expressed by the formula tb^4. If b is doubled, the new cost Q is what percent of the original cost?  Options
A) q = 200
B) q = 600
C) q = 800
D) q = 1600
E) q = 50

Rationale: "original cost c 1 = t 1 * b 1 ^ 4 new cost c 2 = t 2 * b 2 ^ 4 . . . . only b is doubled so t 2 = t 1 and b 2 = 2 b 1 c 2 = t 2 * ( 2 b 1 ) ^ 4 = 16 ( t 1 * b 1 ^ 4 ) = 16 c 1 16 times c 1 = > 1600 % of c 1 ans d = 1600"
Answer: D