PLEASE HELP

The relationship between altitude and the boiling point of a liquid is linear. At an altitude of 8100 ​ft, the liquid boils at 197.04°F. At an altitude of 4500 ​ft, the liquid boils at 202.8°F. Write an equation giving the boiling point b of the​ liquid, in degrees​ Fahrenheit, in terms of altitude​ a, in feet. What is the boiling point of the liquid at 2300 ​ft?

Write an equation.
b= ??