A travel agent offers a vacation plan which costs 'a' dollars for the first day, and a/8 for each additional day. How much does a vacation of b days cost, where b > 1.
Pick one:
A) (ab+7a)/4	B) (ab+8a)/8	C) (ab+a)/8	D) (ab+7a)/8	E) (ab+7a)/7
Cost = a + (b-1)*a/8 = (8a + (b - 1)*a)/8 = (ab+7a)/8   Answer is (ab+7a)/8
<result>D</result>
A travel agent offers a vacation plan which costs 'a' dollars for the first day, and a/8 for each additional day. How much does a vacation of b days cost, where b > 1.