25 01 50 K The management of a department store is interested in estimating the difference between the mean credit purchases of customers using the store's credit card versus those customers using a national major credit card. You are given the following information. Assume the samples were selected randomly. Store's Card Major Credit Card Sample size Sample mean 64 49 $120 Population standard deviation $15 $105 $6 A 95% confidence interval estimate for the difference (Store's Card -Major Credit Card) between the average purchases of the customers using the two different credit cards is a. $49 to $64 b. $105 to $120 c. $6 to $15 d. $10.96 to $19.04