A photocopy store advertises the following prices: 5/c per copy for the first 20 copies, 4/c per copy for the 21st through 100th copy, and 3/c per copy after the 100th copy. Let x be the
number of copies, and let y be the total cost of photocopying. (a) Graph the cost as x goes
from 0 to 200 copies. (b) Find the equation in the form y = mx + b that tells you the cost
of making x copies when x is more than 100.