Cost is expressed by the formula tb^4. If b is doubled, the new cost E is what percent of the original cost? Choose the most appropriate option:
A) e = 200
B) e = 600
C) e = 800
D) e = 1600
E) 50

Rationale: "original cost e , 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