maximum contaminant levels (mcls) are regulations on water quality set by the united states environmental protection agency. researchers measured the chloramines mcls (in mg/l) of water samples from random locations of each of two wells. the data are given below. sample size sample mean sample sd well a 15 3.7 0.3 well b 19 3.4 0.6 assume normal populations with equal variance and construct a 95% confidence interval for the difference in mean mcls levels. find the upper bound of the confidence interval (round off to second decimal place).