A contractor purchases gravel one cubic yard at a time.

(a) A gravel driveway $L$ yards long and 3 yards wide is to be poured to a depth of 1 foot. Find a formula for $n(L)$, the number of cubic yards of gravel the contractor buys, assuming that he buys 10 more cubic yards of gravel than are needed (to be sure he'll have enough).
$n(L) =$ cubic yards help (formulas)

(b) Assuming no driveway is less than 3 yards long or more than 12 yards long, find the domain and range of $n(L)$. Enter your answers as comma separated lists of numbers.
Domain: help (numbers)
Range:   help (numbers)

(c) Assuming that no driveway is less than 3 yards long or more than 12 yards long, sketch a graph of $n(L)$. Which graph A-D below most closely matches the graph you drew? ? A B C D

A		B		C		D

(Click on a graph to enlarge it.)