(1] Suppose that the probabilityr density function f(:1:) of the length X of an international phone call1 rounded up to the next minute, is given by: ----n mmm (a) Calculate P[X 5 2), P(X a: 2), and PHI :3 1). (b) Plot the cumulative distribution function Flfa'). (c) Calculate the mean a = E[X ). (d) Calculate EU?) and us it to compute the variance o2