21.36 two marketing strategies. credit card companies earn a percent of the amount charged on their credit cards, paid by the stores that accept the card. a credit card company compares two proposals for increasing the amount that its customers charge on their credit cards. proposal 1 offers to eliminate the annual fee for customers who charge $1800 or more during the year on their card. proposal 2 offers a small percent of the total amount charged as a cash reward at the end of the year. the credit card company offers each proposal to an srs of 100 of its existing customers. at the end of the year, the total amount charged by each customer is recorded. here are the summary statistics. group proposal 1 proposal 2 100 $1319 $261 100 $1372 $274 (a) do the data show a significant difference between the mean amounts charged by customers offered the two proposed plans? give the null and alternative hypotheses, and calculate the two-sample t statistic. obtain the p-value, using option 2. state your practical conclusions. (b) the distributions of the amounts charged on credit cards are skewed to the right. however, outliers are prevented by the limits that the credit card companies impose on credit balances. do you think that skewness threatens the validity of the text that you used in part (a)? explain your answer.