Answer: 1. 360. 2. t < 40.
Explanation:
1. Let d = to the amount the shopper spends. d has to be greater than 400. If the shopper spends more that 400, then he will pay 400 x 0.9 = 360.
2. Since t can't be more than 40, it must be less than 40. So t < 40.