On a Physical Fitness Test Middle School Boys Are Awarded $$18 + 34 = 52$$

Multiple Choice

On a physical fitness test middle school boys are awarded one point for each push-up they can do,
And a point for each sit-up. National results showed that boys average 18 pushups with a standard
Deviation of 4 push-ups, and 34 sit-ups with standard deviation 11. The mean of their combined
(total) scores was therefore 1 $$18 + 34 = 52$$
Points. What is the standard deviation of their combined
Scores?

A) 15
B) 137
C) cannot be determined
D) 11.7
E) 5.3