4. (12 points) A candy manufacturer selects mints at random from the production line and weighs them. For one week the day shift weighed nj - 194 mints and the night shift weighed n2 = 162 mints. The numbers of these mints that weighed at most 21 grams was y1 - 28 for the day shift and y2 - 11 for the night shift. Let p1 and p2 denote the proportions of mints that weigh at most 21 grams for the day and night shifts, respectively. (a) (4 points) Give a point estimate of p1. (b) (4 points) Give the endpoints for a 95% confindence interval for p1. (c) (4 points) Give a point estimate of p1 - p2. (d) (4 points) Find a one-sided 95% confidence interval that gives a lower bound for p1 - p2