Please provide detail solution, thx

3. (10 points) Suppose that you have the numbers {-50, -49, . .., 49,50}. You're going to succes- sively choose numbers without replacement from this set and call them X1, X2, X3. ..., X101. (a) (5 points) Show that for every i between 1 and 101, Var(Xi) = 850. You may find the sum of square formula helpful: k2 = n(n+1)(2n+1) 6 (b) (5 points) Show that for any i / j between 1 and 101, Cov(Xi, X;) = -8.5. (Hint: Use that Var(X1+ X2+.. .+ X101) =0) (why is this true?) and expand out the left hand side using the formula for the variance of the sum of not necessarily independent random variables