7. Let X be a continuous random variable with probability density function f(x) = 16 VT for O E r S 4, 0 elsewhere. (a) Give the complete description of the cumulative distribu- tion function F(r) as a piecewise defined function. (b) Find E(X ) and V(X). (c) Find P(X 2) without doing any calcula- tions. 8. Consider the following probability density function: f(x) = 2(x - 1) for 1 E x $ 2, elsewhere. (a) Find E(X) and V(X). (b) Find the 75th percentile of this distribution. 9. Suppose the following is a cumulative distribution func- tion: 0 if a