With the arrival of the horse race winter season

With the arrival of the horse race winter season, five jockeys were informed that the owner of the stable had bought 25 new horses. One of the jockeys estimated the following probability distribution of X, the total number of horses he could ride during the first week of the season.

X 0 1 2 3 4 
P(X) .05 .15 .35 .25 .20 

(a.)  What is the weighted average of the number of horses that could be ridden by the jockey in the first week of the season?

(b.)   What is the standard deviation?