The cost of mailing a package weighing up to, but not including, 1 pound is $2.72. Each

Question:

The cost of mailing a package weighing up to, but not including, 1 pound is $2.72. Each additional pound or portion of a pound costs $0.50.
(a) Use the greatest integer function to create a model for the cost C of mailing a package weighing x pounds, where x > 0.
(b) Sketch the graph of the function?