Stuck on this:

4. Let X1, X2, ... Xn be a random sample from a population with probability density function: X+6 3 if x > - 6 f (x ) = 3 0, otherwise Let X = =>t=1Xi, S= 2X2+55 Un-121=1(Xi - X)2 and T = 41X |+354 (a) Show that X converges in probability to some constant and find the constant; (b) Show that S' converges in probability to some constant and find the constant; (c) Show that T converges in probability to some constant and find the constant