Suppose f(x, y)=(x−y)(4−xy). answer the following. 1. find the local maxima of f. list your answers as points in the form (a, b,c). answer (separate by commas): 2. find the local minima of f. list your answers as points in the form (a, b,c). answer (separate by commas): 3. find the saddle points of f. list your answers as points in the form (a, b,c). answer (separate by commas):