4: In 2013, the United States Postal Service charged $0.46 to mail a letter weighing up to 1 oz. and $0.20 per ounce for each additional ounce. Which function would determine the cost, in dollars, c(z), of mailing a letter weighing z ounces where z is an integer greater than 1

c(z) = 0.46 + 0.20(z - 1)

Explanation:

For letters weighing up to 1 oz $0.46 is charged

For each additional ounce $0.20 is charged

so base cost is $0.46 which should remain constant and should not change.

variable cost is $0.20 which can change according to weight so it should be linked with variable z.

So the required function would be

c(z) = 0.46 + 0.20(z - 1)

Verification:

Lets verify the above function.

When weight of the letter is 1 oz.

c(1) = 0.46 + 0.20(1 - 1) = 0.46 + 0.20(0) = $0.46

When weight of the letter is 2 oz.

c(2) = 0.46 + 0.20(2 - 1) = 0.46 + 0.20(1) = $0.66

Hence the function is working correctly.