Which set of numbers is not in the solution set of the inequality x < 12?

a
{−4, −3, 2, 3, 6}
b) {−1, 3, 5, 7, 9}
c) {1, 2, 5, 6, 11}

d) {1, 9, 10, 15, 17}

Im pretty sure the answer is D) 1,9,10,15,17

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).