The rate at which water evaporates from a certain reservoir depends on the air temperature. The table below shows the number of acre-feet (af) of water per day that evaporate from the reservoir for various temperatures in degrees Fahrenheit.
Temperature, °F af
40 760
60 1600
70 2020
85 2650

(a) Find a linear model for the number of acre-feet of water that evaporate as a function of temperature.
E(T) =
(c) Assuming that water continues to evaporate at the same rate, how many acre-feet of water will evaporate per day when the temperature is 75°F?

Question

The rate at which water evaporates from a certain reservoir depends on the air temperature. The table below shows the number of acre-feet (af) of water per day that evaporate from the reservoir for various temperatures in degrees Fahrenheit. 
Temperature, °F  af  
40  760  
60  1600  
70  2020  
85  2650

(a) Find a linear model for the number of acre-feet of water that evaporate as a function of temperature.
E(T) = 
(c) Assuming that water continues to evaporate at the same rate, how many acre-feet of water will evaporate per day when the temperature is 75°F?