Which of the following are valid probability density functions? Select one or more: fx(x) gx(x) hx(x) 0 otherwise 2x/3 otherwise 0 0 otherwise Which of the following are valid cumulative distribution functions? Select one or more: 0 otherwise 0 Gx(x) 1 o otherwise Find the median of the random variable X Answer: Exp(l) (i.e. with pdf fx(x) = for > 0 and fx(x) 0 othewise), and enter it as a decimal number with 3 decimal places.