Question in mechanical engineering

Q.16 The length, width and thickness of a steel sample are 400 mm, 40 mm and 20 mm. respectively. Its thickness needs to be uniformly reduced by 2 min in a single pass by using horizontal slab milling. The milling cutter (diameter: 100 mm, width: 50 mm) has 20 teeth and rotates at 1200 rpm. The feed per tooth is 0.05 mm. The feed direction is along the length of the sample. If the over travel distance is the same as the approach distance, the approach distance and time taken to complete the required machining task are (a) 14 mm, 21.4 s (b) 21 mm, 39.4 s (c) 14 mm, 18.4 s (d) 21 mm, 28.9 s