Solve the Problem $$\text { quadratic mean } = \sqrt { \frac { \sum x ^ { 2 } } { n } }$$

Multiple Choice

Solve the problem.
-The quadratic mean (or root mean square) is usually used in physical applications. In power distribution systems, for example, voltages and currents are usually referred to in terms of their root mean square value. The quadratic mean of a set of values is obtained by squaring each value, adding the results, dividing by the number of values (n) , and then taking the square root of that result, expressed as $$\text { quadratic mean } = \sqrt { \frac { \sum x ^ { 2 } } { n } }$$ Find the root mean square of these power supplies (in volts) : 19, 57, 28, 45.

A) 20.0 volts
B) 37.2 volts
C) 74.5 volts
D) 40.1 volts