8. You would like to create an enclosed area for your dog in your backyard. To this end, you have bought 30 yards of fencing. Furthermore, you would like to create the enclosure so that part of the back wall of your house serves as a wall for the enclosure. Determine the dimensions that yield the maximum area. 9. Given m(r)=3r-5, find and simplify the difference quotient (r+h)-m(r) 22. The cost, in dollars, of producing x units of a certain commodity is C(x)=920+2x-0.02x²+0.00007x' a) Find the marginal cost function. b) Find C'(100) and explain its meaning.