The number of ships to arrive at a harbor on any given day is a random variable represented by x. The probability distribution of x is as follows. (Give your answers correct to two decimal places.)

col1 x 10 11 12 13 14
col2 P(x) 0.37 0.07 0.11 0.13 0.32
(a) Find the mean of the number of ships that arrive at a harbor on a given day
(b) Find the standard deviation, ?, of the number of ships that arrive at a harbor on a given day.