Find the mean and standard deviation for a random variable X

Find the mean and standard deviation for a random variable X having the following CDF:

F(x) = {
0, x < 3
3/8, 3 x < 1
11/16, 1 x < 5
1, x 5

Solution

as the function takes different values for differeny values of x

bt the values of f(x) are 0,3/8,11/16,1

so the mean will be 0+3/8+11/16+1 = 33/16=0.6875

standard deviation = will be =0.3125