3-6. Listed below are some changes in (shifts in) demand for various items. In each case, the change in demand has been caused by a change in the price of a substitute or of a complement. Explain whether the price of the substitute or complement must have increased or decreased. a. A rise in the demand for a dashboard global- positioning-system device follows a change in the price of automobiles, which are complements. b. A fall in the demand for e-book readers follows a change in the price of e-books, which are complements. C. A rise in the demand for tablet devices follows a change in the price of ultrathin laptop comput- ers, which are substitutes. d. A fall in the demand for physical books follows a change in the price of e-books, which are substitutes