If the temperature outside is 86°F, the heat index can be found using the equation y = 0.004x2 − 0.1243x + 84.028. This equation is also the curve of best fit for the values in the table. In the equation, x represents the relative humidity and y represents the heat index. Relative Humidity Heat Index
40% 85°F
55% 89°F
75% 97°F
90% 105°F
100% 112°F

Using the curve of best fit, if the current temperature is 86°F and the relative humidity is 55%, what is the heat index? Round the answer to the nearest degree.

A.
78°F
B.
88°F
C.
89°F
D.
90°F