Which of the following is a linear demand function, where x denotes the multiplication, PX is the price of good X, PY is the price of good Y, QdX is the quantity demanded for good X and M is the income, Msq denotes the square of M, Hsq denotes the square of H, x denotes the multiplication and the multiplication operator x has priority over addition.

Select one:

a.QdX equals to 0 plus a x PX plus b x PY plus c x M plus e x H.

b.None.

c.QdX equals to x PX x a x PY x b x M x c x H x e.

d.QdX equals to 0 plus a x PX x PX plus b x PY x PY plus c x Msq plus c x Hsq.

e.QdX equals to plus a x log PX plus b x log PY plus c x log M plus c x log H.