For price discrimination via coupons to be successful, it must be TRUE that:
a. shoppers who use coupons have more elastic demand than shoppers who do not.
b. shoppers who use coupons have more inelastic demand than shoppers who do not.
c. there is a negative correlation between coupon use and the consumer's willingness to shop for price.
d. firms can directly identify which consumers are the most price sensitive before purchase of the good.