A cable that weighs 6 lb/ft is used to lift 750 lb of coal up a mine shaft 350 ft deep. Find the work done. Show how to approximate the required work by a Riemann sum. (Let x be the distance in feet below the top of the shaft. Enter xi* as xi.) lim n→∞ n Δxi = 1 Express the work as an integral. 0 dx Evaluate the integral.