The random process Z(t) is defined as:
Z(t) = 2Xt - Y,
where X and Y are a pair of random variables with means mX and mY, variances σ^2X and σ^2Y, and correlation coefficient ρ.
(a) Find the mean function and autocorrelation function of the random process Z(t).
(b) Find the pdf of the random process Z(t) if X and Y are jointly Gaussian random variables.