Public debt in example 5 of section 2.3, the federal debt held by the public as a percent of the gross domestic product (gdp) was modeled by the function
y=0.00630t^3-0.289t^2+4.00t+25.3
where t was the time (in years) since 1980. source: budget of the u. s. government.
(a) find the average public debt, as a percent of gdp, from 1990 to 2000.
(b) find the average public debt, as a percent of gdp, from 2000 to 2015.