Suppose we divide the time interval [0, t] into n equally spaced periods so that ?t = t/n. Consider a particle doing a random walk, starting from X0 = 0, and within each period i = 1, 2, ..., n, the particle moves by Zi, so that Xt = nX i=1 Zi, and Zi = ??t + ???t?i, where E(?i) = 0 and Var(?i) = 1, and ?i are independent. ? and ? are constants. (1) Calculate E(Zi) and Var(Zi). (2) Calculate E(Xt) and Var(Xt). Do they depend on n? (3) For large n, what is the approximate distribution of Xt? 2