So you would plug in 0 for a from the beginning since this is numerical slope definition of a derivative
Box 1) (LxW) 20x6=120
box 2) (LxW) 15x4=60
box 1 cost) (size of box x price of box) 120x1.25=150
box 2 cost) (size of box x price of box) 60x1.25=75
subtract 150 and 75 to get 75
answer: the company is saving $75 by choosing to make 50 of box 2 instead of 50 of box 1
hope this makes sense comment if you need more explanation
The answer is -6 because the square root of 36 is 6, but then you have to add the negative in front of it.
