The length, width and thickness of a steel sample are 400 mm, 410 mm, 40 mm and 20 mm, respectively. I ts thickness needs to be uniformly reduced by 2 mm in a single pass by using horizontal slab miling. The miling 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 t he required machining task are:

• A. 21 mm, 39.4 s
• B. 14 mm, 18.4 s
• C. 14 mm, 21.4 s
• D. 21 mm, 28.9 s