The manager of a mail order business will ship the packages to their customers. The cost, in dollars, to mail a package is based on its weight x, in pounds, and is given by the equation y = 0.7x2 - 2.5x + 3. How much will the cost be to mail a 5 lb. package?

To determine the cost of the mail, we simply substitute the mass of the package to the given function. Mathematical functions are used to relate two variables, observing how changing one variable affects the other variable. For this case, the cost of a mail and the weight of the package are related by the function y = 0.7x2 - 2.5x + 3 where x represents the mass in units of pounds (lb) and y is the cost in units of dollars ($). We calculate cost as follows:

y = 0.7x^2 - 2.5x + 3

y = 0.7 (5) ^2 - 2.5 (5) + 3

y = 8 dollars

Therefore, the cost of mailing a 5 lb package would be 8 dollars.