Answer:
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.