Let C ( t ) = 0.021 t 2 + 0.22 t + 53.292 be the capacity (in percent) at which U.S. nuclear power plants are working t years after 1970. Estimate at what capacity (in percentage) U. S. nuclear power plants were working in 1994. Round to the nearest whole percent. Predict in which year U. S. nuclear power plants will be working at full (100%) capacity.