According to the U.S. Census Bureau, the relation between the average annual earnings of males and females with various levels of educational attainment can be modeled by the function

F = 0.78M - 1.316

where M and F represent the average annual earnings (in thousands of dollars) of males and females, respectively.

(a) Viewing F as a function of M, what is the slope of the graph of this function?

(b) Interpret the slope as a rate of change.

(c) When the average annual earnings for males reach $60,000, what does the equation predict for the average annual earnings for females?