Randi and Leah are studying together for an exam. Let X represent the number of hours Randi spends studying nightly, and let Y represent the number of hours Leah spends studying nightly. The mean of X is 4.5 hours with a
standard deviation of 1.1 hours and the mean of Y is 3.7 hours with a standard deviation of 1.8 hours. Assuming these are independent random variables, which answer choice correctly calculates and interprets the standard
deviation of the sum, S = X + Y?