Engineers sometimes add chlorine to pipes to disinfect water. It is desired to achieve four logs of kill. This means that the effluent concentration of microorganisms is 10-4 times the influent. If the flow is 40 ft3/min, calculate the volume of the pipe required to achieve four logs of kill if the first-order rate constant for disinfection is 0.5 min-1. If the pipe is 3 feet in diameter, how long would the pipe have to be?