For each residual plot below, determine whether a linear model is appropriate, and if not, why not. 15 20 10 10 5 10 15 Residuals Residuals -10 -20 20 0 30a 40 50 -5 -30 -10 40 X X Pick Pick 10 0 20 60 80 Residuals -5 -10 -15 X Pick