Notice that in the diagram in Exercise 15.27 SuppTotl has both a direct and an indirect effect on Depression. Its direct effect is the arrow that goes from SuppTotl to DepressT. The indirect effect (which here is not significant) comes from the fact that SuppTotl influences PVLoss, which in turn affects DepressT. Explain these direct and indirect effects in terms of semipartial regression coefficients.