Product of mining tailings, the concentration of harmful minerals in the river Granillo has increased during the last three decades. Concerned about the quality of water from this river to be used as drinking water, a group of students took samples of the amount of calcium present in the water (mgr/It) and obtained the following results: 12,9 12,7 18,6 13,7 9.7 12,6 14.5 12,8 15,3 10,6 7,3 12,4 5,3 7,9 9,3 5,9 8,3 9,0 4,4 15,9 15,7 17,5 4,2 10,8 If it is considered feasible to use water with a concentration of up to 9 (mg/It) a) Assuming that the necessary assumptions are fulfilled, analyze with a significance of 1% if there is sufficient statistical evidence to indicate that the river water is viable to be used as drinking water. b) Does your answer change if you use a significance of 0.5%? Justify. c) Estimate with 90% confidence the mean value of the calcium content in the river Pimple (Confidence Interval)