Alcohol is removed from the body by the lungs, the kidneys, and by chemical processes in liver, At moderate concentration levels, the majority work of removing the alcohol is done by the liver, less than 5% of the alcohol is eliminated by the lungs and kidneys. The rate r at which the liver process alcohol from the bloodstream is related to the blood alcohol concentration x by a rational function of the form `r(x)=(ax)/(x + beta)` for some positive constants a and b. Find the maximum possible rate of removal.