(b) (d) The amount Of water to use is from 100 Thc SR cost function is then: cSR(y) = + 100 50 The of" = 100 is C(IOO) = The CONSTANT. f(XX1, = The long run cost is found by setting: _i .t2 = 2$1 Substitute this into the production function and The cost function is This production function has constant returns to scale: f(XX1, = Thc constant returns to implies that the AC is flat.