There are three reactors degrading a chemical biologically, at three degradation rates; i.e., 0.2 d^-1, 0.4 d^-1, and 1.0 d^-1. The residence time of the chemical in these reactors are 10 d, 5 d, and 55 d, respectively. Which reactor is more efficient and why? If all these are CMFR reactors, how can you increase the performance of the least efficient reactor?