The heights of females in the United States are approximately normally distributed with a mean of 63.8 inches and a standard deviation of 2.8 inches and the heights of males are approximately normally distributed with a mean of 69.3 inches and a standard deviation of 3.0 inches. 

a. If we were to randomly choose one U.S. male and randomly choose one U.S. female, define S to be the sum of their two heights. What are the mean and the standard deviation of S? 

b. What are the mean and standard deviation of the sum of the heights of two randomly chosen males and two randomly chosen females in the United States? 

c. What are the mean and standard deviation of the sum of the heights of three randomly chosen males and two randomly chosen females in the United States?