This problem exhibits exponential growth since the GDP grows at the same rate every year. The equation would follow this format:
G = G0(1+r)t 
G represents present GDP, G0 represents initial GDP, r represents the rate of increase in decimal form, and t represents time. In this case the equation would be:
2800 = 577(1+.032)t or
2800 = 577(1.032)t
Solve for t
2800/577 = 1.032t
4.853 = 1.032t
log 4.853 = t*log 1.032
t = (log 4.853)/(log 1.032) = 50.15 years
This means that approximately 50 years after 1985, the GDP will be $2.8 trillion. That year would be 2035.