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?

subscript u s=0.7; Randi and Leah can expect the total number of hours spent studying to vary by approximately 0.7 hours from the mean.

subscript s = 1.7; Randi and Leah can expect the total number of hours spent studying to vary by approximately 1.7 hours
from the mean.

subscript s=2.1; Randi and Leah can expect the total number of hours spent studying to vary by approximately 2.1 hours from the mean.

subscript = 2.9; Randi and Leah can expect the total number of hours spent studying to vary by approximately 2.9 hours
from the mean.