In a bord and pillar panel six shuttle cars, each of 10 tonne capacity, are deployed to transport coal produced by two continuous miners to a belt conveyor. Each shuttle car on an average carries 80% of its rated capacity and makes 7 round trips in an hour. The belt conveyor has a capacity such that the effective material cross section area is of 0.09 m² and runs at a speed 1.1 m/s. The broken coal has a bulk density of 1.2 tonne/m³. The ratio between the production and the capacity of the belt conveyor, in percent is