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4.5. After tting the regression model, Y=50+1x1+132x2 +3x3+e on 15 cases, it is found that the mean square error 32 = 3 and 0.5 0.3 0.2 0.6 0.3 6.0 0.5 0.4 0.2 0.5 0.2 0.7 0.6 0.4 0.7 3.0 (X'Xr' = Find a. The estimate of V(Bl). b. The estimate of Cov(31, 5'3). c. The estimate of Corr(31, 33). d. The estimate of VG}; 33)