1) A ball mill with a gape diameter of 2.0 m and a ball diameter of 50 mm is used to grind 3.5 metric tons of granite. What is the critical speed of that mill? 2) What speed range do you recommend for a coarse grind? 3) Consider that the granite being fed in the ball mill has an average rock size of 600 m and is being ground down to 100 m. How much energy will be required to grind the entirety of the granite? Reminder: Wi(granite) = 15.13 4) A second grinding is done in a similar ball mill, except the ball diameter is now 10 mm. We want abrasive grinding. What speed range would you recommend?