A planer has a 10-hp motor, and 75% of the motor output is available at the cutting tool. The specific power for cutting cast iron certain metal is 0.03 W/mm3 or .67 hp/in3/min. What is the maximum depth of cut that can be taken in shaping a surface in this material if the surface is 305 × 305 mm (12 × 12 in.), the feed is 0.25 in. per stroke, and the cutting speed is 54.9 mm (180 ft) per minute?