Any integer may be reduced to a single digit by the method illustrated below. 51-5+1-6 58-5+8 13-1+3-4 The random variable D denotes the digit that results from the reduction of an integer, selected at random, from the twenty integers 50, 51, 52, ..., 69.

(a) Show that P(D-5)=0.15

(b) Determine the probability for each of the other possible values of D.

(c) Calculate the expected value of D.

(d) Calculate, to two decimal places, the variance of D. (NEAB)