sorry if wrong
Metal removal rate in turning is how much material is removed from the work piece . In this case , your cutting speed ,feed, depth of cut all describe factors that affect the metal removal rate.
The metal removal rate of turning is equal to the cutting speed (2500 mm/s) ,multiplied by the depth of cut (3mm) ,multiplied by the feed (0.4mm/rev) . This gives us a metal removal rate of 30 mm3 per second