The probability distribution of x, the number of imperfections per 10 meters

The probability distribution of X, the number of imperfections per 10 meters of a synthetic fabric in continuous rolls of uniform width, is given by the accompanying table. Find the average number of imperfections per 10 meters of this fabric. x 0 1 2 3 4 :1- f(x) 0.43 0.39 0.11 0.05 0.02