A 20° involute pinion has 22 teeth, 3.5 mm module, the form factor as 0.28 and allowable stress as 42 MPa. The gear of same material as gear transmits 6 kW of power at 4900 rpm and incremental load in gear tooth due to dynamic effect is 490 N. The minimum face width of pinion tooth for safe gear and pinion mesh design will be ________ mm (Give the answer in the integer form)