What is the probability that the number of lines in use is farther than 3 standard deviation from the mean value?

A business has six customer service telephone lines. let x denote the number of lines in use at any given time. suppose that the probability distrubution of x is as follows: x : 0,1 ,2,3,4,5,6 p(x): 0.10,0.15,020,025,0.20,0.06,0.04