Question

The table below shows the cost of mailing a first-class letter with the United States Postal Service in November 2006. The postage cost is a function of the weight of the letter.
First Class Postage Rates
Weight
(ounces)

Cost
1

$0.39
2

$0.63
3

$0.87
4

$1.11
5

$1.35




Refer to the table above. Write an expression that can be used to find the cost of mailing a letter that weighs n ounces.