I'm assuming that you want to find the maximum point for the cost function given by ... W(x) = -0.1x2 + 16x + 7666
I'm a;so assuming that you might not have taken calculus (yet), but that's no biggie.....we can do this without calculus.
For any quadratic function given by ax^2 + bx + c, the maximum "x" value on the curve is given by .......x = -b / 2a. (When - or if - you take calculus, you'll see why this is true.)
So anyway, the maximum "x" value (representing the number of units that maximize the cost) in our case is given by.....
x = -16 / 2 (-.1), where "b" = 16 and a = (-.1)
So x = -16 / (-.2) = 80
Then 80 units maximize the cost.....and since it appears that you know how to plug this into the cost function, I'll let you finish up. The answer that you get is the max cost in dollars.
Hope this helps....happy motoring !!!
+128707 
