This is about time serie questions, if u know can you show all the steps for me ,thanks.

Question 1: A step spectral distribution function can be expred using a general linear cyclical model M Z: = 2444 SiiEr-l'it + Bi] li=1 where A,- are constants, 8.; are iid Unifmn(7r,1r), a11- are distinct frequencies contained in the interval [rr, W], and M is the number of known steps. a. Dbtain the mean of 3:. b. Dbtain the covariance function of lag is. c. Obtain the correlation function of lag k