If the excavation diameter of the shaft is 5.0m, allowable time for mucking is 5.0hr per shift and the advance rate of shaft sinking is one round of 3.0m per shift, calculate the bucket size required for the mucking unit. (Requirements: (1) Need consider an adequate swell factor for rock fragmentation and apply it correct in calculation (applying swell factor correctly, 1 marks). (2) Need detail the circle time composition for mucking and hoisting (main calculation part, 2 marks). (3) Need use efficiency hour for the bucket productivity (applying efficiency hour correctly, 1 mark).