Table 1 shows values of the breakage distribution function b(i,k) and breakage selection function Sk for the grinding of an ore in a ball mill. The unit time is based on 10 minutes in the mill at a particular speed. (a) Determine the expected size distribution of the product resulting from the milling of the feed material, with composition given in Table 1 , after 10 minutes in the mill at the same speed. (b) Use a suitable grinding law to estimate the energy required to grind 200 tonnes of the ore using the mill. According to the manufacturer of the mill, the energy used in milling the same material from 300m to 150m is 3.2kWh/ tonne using the same milling machine. (c) Grinding is done in a closed-circuit milling system. An installed cyclone classifier separates the mill output and returns all material larger than 150m back to the mill for regrinding. The undersized material is fed to the processing unit at a rate of 120 tonnes/h. Determine (i) the rate of oversized material returned for re-grinding in tonnes/h, and (ii) the grinding power for the ball mill (in kW ). Table 1: Results of mill test