Use the Following General Linear Demand Function Below $Q _ { d } = a + b P + c M + d P _ { R }$

Multiple Choice

Use the following general linear demand function below: $Q _ { d } = a + b P + c M + d P _ { R }$ where Q_d = quantity demanded,P = the price of the good,M = income, $P _ { R}$ = the price of a good related in consumption.If c = 15 and d = 20,the good is

A) a normal good.
B) an inferior good.
C) a substitute for good R.
D) a complement with good R.
E) both a and c