Let w = weight of any additional ounce or fraction of an ounce
P(w) = .39 + .24w
.39 for every letter 13 ounces + .24 for each additional ounce or fraction of an ounce.
I need help with this problem, maybe I'm overthinking it...
The domestic postage rate for a letter weighing 13 ounces or less was 39 cents for a letter weighing one ounce or less plus 24 cents for each additional ounce (or part of an ounce). Write postage P (cents) as a function of the weight w (ounces) of a letter.