a} Represent the predicted value 17}, as a linear function of the observations 1',13,...,}; and derive the mean and variance of 1% using the fact that for an}.r constants a1,az,...,an and independent observations Y,I,...,I; where I\"; ~ Ngupo'fl), E'lz gig} : Edi-Jul and V'lZani} : Ear-20}? i=1 i=1 i=1 i=1 b) Show the steps to conclude under normality of errors that it as; +51%) ~ t , (H: 35?. l where {(#2) represent the student's trandom variable 1with (n-Z) degrees of 'eedorn. C) Use the formula for 0'2 {ii} to derive the expression for 0'2 {b0}