If the temperature drops from 9°F to −19°F, by how much did the temperature decrease? The students came up with different answers. Johnelle said the answer is 10° F, and Mark said the answer is 28°F. Which choice best explains who is correct and why?

a. Johnelle is correct because the absolute value of |19 − 9| is 10.
b. Johnelle is correct because the absolute value of |−19−9| is 10.
c. Mark is correct because the absolute value of |−19 + 9|is 10
d. Mark is correct because the absolute value of −|−19+9| is 10