100
                                In March 1991, the U.S. Post Office was charging $1.73 for an airmail letter weighing 2 ounces to any country other than Canada or Mexico.  Each additional 1/2 ounce, or part thereof, cost 39 cents.  Write the equation for the function that gives the cost C of an international airmail letter weighing 2 oz or more?
                                What is C=1.73+.39[w - 2]