12-7. An incinerator that normally burns waste with a heating value of 700 to 1,000 Btu/lb. and is designed to handle 2 x 10^7 Btu/h must burn a rubber waste with a heating value of 12,000 Btu/lb. Estimate the maximum size of a waste batch for this system to perform effectively. Assume the residence time in the incinerator is 6 min.