A graphing calculator is recommended. A 10-gallon barrel is filled completely with pure water. Salt water with a concentration of 0.3 lb/gal is then pumped into the barrel, and the resulting mixture overflows at the same rate. The amount of salt in the barrel at time t is Q(t)=3(1 e 0.09t) where t is measured in minutes and Q(t) is measured in pounds. (a) How much salt is in the barrel after 9 min? (Round your answer to two decimal places.) lb (b) How much salt is in the barrel after 18 min? (Round your answer to two decimal places.) lb