Answer
Grading Scales, Cost of Shipping a Package
Work Step by Step
Grading scales: Although a grade can be anywhere between 90% and 100%, it will regardless be considered an "A". Likewise, grades between 80% and 90% will be considered a "B". Plotting this on a graph, we see that the range of grades for a specific letter grade will form horizontal lines.
Shipping costs: At many post offices, shipping is priced such that a flat rate will be charged if the package is below a certain rate, and another rate is charged if the package is between another two ranges of weight. This also forms horizontal lines, as the weight can change ($x$-value) but the price ($y$-value) will remain the same.
