Disposable income, the amount left after taxes have been paid, is one measure of the health of the economy. Using U.S. Energy Information Administration data for selected years from 2015 and projected to 2040, the U.S. real disposable income per capita (in dollars) can be approximated by the equation

I = 707.6t + 39,090

where t is the number of years after 2015.

(a) What t-value corresponds to 2023?

(b) Find the predicted U.S. per capita real disposable income (to the nearest $10) in 2023.

(c) In what year is the U.S. per capita real disposable income expected to exceed $55,000?