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

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.For the general linear demand function given above

A) $\Delta Q _ { d } / \Delta M = c$
B) d is the effect on the quantity demanded of the good of a one-dollar change in the price of the related good,all other things constant.
C) b is the effect on the quantity demanded of the good of a one-dollar change in the price of the good,all other things constant.
D) all of the above