In Problem 3.8, you used multiple linear regression analysis to conclude that urinary calcium UCa was significantly related to dietary calcium DCa and urinary sodium UNa, but not to dietary protein Dp or glomerular filtration rate Gfr. This conclusion assumes that there is no serious multicollinearity. Evaluate the multicollinearity in the set of four independent variables used in that analysis. (The data are in Table D-5, Appendix D.)