3) Let the prices of two goods x and y be px and py respectively, and let income be m. For which of the following demand functions is x a complement to y ? a. x(px,py,m)=pxm+py b. x(px,py,m)=pxpy4m2 c. x(px,py,m)=mpxpy2 d. x(px,py,m)=pxmx e. None of the above..