Need a detailed explanation please!

A public health official claims that the mean home water use is 350 gallows a day, To verify this claim a study of 20 randomly selected homes was investigated with the result that the average daily water uses of these 20 homes were as follows : 340, 3.56, 332, 362, 318, 344, 386, 402, 328,360, 362, 354, 340, 372, 338, 375, 364, 355, 324, 370 2) Do the data contradict the official's claim. - 3 - Use the 10 percent level of significance Confirm your decison by using the p-value. b) Find 90 percent confidence interval for the mean home water use assuming that is unknown