4. a) Marginal profit is P' = 6x +5. Find the accumulated profit (change in profit) when the units x increase from 8 to 12. P= 12 (6x+5) 2x = 6X X=/2 +5x 12 X = g 2 = 3x +5x X=8 & = ) 3 ( 12 ) + 5 ( 12) - 3 (8) 2 + 5 ( 8)] = 3 ( 144)+60 - 3 (64)+40) => 432+60- (192+ 40 ) = 492- 232 = 260 b) Find the area under the curve y=-ter*+ vx and bounded below by the x axis for X 1 x