The concentration of mercury in a lake has been monitored for a number of years. Measurements are taken on weekly basis yielded an average of 1.2mg/m3(population mean). Following an accident at a smelter on the shore of the lake, 15 measurements produced the following mercury concentration 1.60, 1.77, 1.61, 1.08, 1.07, 1.79, 1.34, 1.07, 1.45, 1.59, 1.43, 2.07, 1.16, 0.85, 2.11 a) what assumptions you need to compute a t confidence interval? Can you built a z confidence interval, explain your answer b)Provide a point estimate of the mean mercury concentration after the accident c) regardless of whether or not you think the assumptions are satisfied, construct a 95% confidence interval on the mean mercury concentration after the accident. Interpret this interval d) If you want 95% confidence interval on the mean mercury concentration after the accident with margin of error 0.01, what should be the minimal number of mercury readings you should have