In order to determine the effect their salespersons have on purchases, a department store polled 700 shoppers regarding whether or not they made a purchase and whether or not they were pleased with the service they received. Of those who made a purchase, 151 were happy with the service and 127 were not. Of those who made no purchase, 201 were happy with the service and 221 were not. Use probability rules (when appropriate) to find the probability that a shopper made a purchase