The solution is as follows:
Energy Consumption after 35 years = 400*1000 MW*(1+0.02*35) = 680,000 MW
After 35 years, United States would need 680,000 MW. If the standard -sized power plant has a capacity if 1000 MW, so, you would need:
Number of power plants = 680,000/1000 = 680 Thus, the additional power plants needed would be:
Additional power plants = 680 - 400 = 280 power plants