K brew sells a wide variety of outdoor equipment and clothing. The company sells both through mail order and via the internet. Random samples of sales receipts were studied for mail-order sales and internet sales, with the total purchase being recorded for each sale. A random sample of 13 sales receipts for mail-order sales results in a mean sale amount of $62.00 with a standard deviation of $28.25. A random sample of 9 sales receipts for internet sales results in a mean sale amount of $67.60 with a standard deviation of $19.75. Using this data, don't the 80% confidence interval for the true mean difference between the mean amount of mail order purchases and the mean amount of internet purchases. Assume that the population variances are not equal and that the two populations are normally distributed. Step 3 of 3: construct the 80% confidence interval. Round your answers to two decimal places. Lower endpoint___? Upper endpoint____