Find (, (x.y) and fy(x.y), and explain why f(x,y) has no local extrema. f(x.y) =4.6 -1.3x +7.By + 0.3y"+x f, (x,y) = fy (x,y) = Choose the best explanation below for the reason that f(x,y) has no local extrema. PI O A. The function f(x,y) can never equal zero. .C O B. The function fy(x.y) is always positive while the function fx(x,y) is always negative. C. The function fx (x,y) can never equal zero. O D. The functions f, (x,y) and fy (x,y) are never equal to each other. Irse SU