Could someone show me how to solve this:

Find the maximum and minimum values attained by the function f along the path c(t). (a) f(x, y) = xy; c(t) = (cos(t), sin(t)); 0 t 2 maximum value minimum value (b) f(x, y) = x + y; c(t) = (cos(t), 3 sin(t)); 0 t 2 maximum value minimum value