The overall gear ratio in a 2 stage speed reduction gear box (with all spur gears) is 12. The input and output shafts of the gear box are collinear. The countershafts which is parallel to the input and output shafts of the gear box are collinear. The countershafts which is parallel to the input and output shafts has a gear (Z2 teeth) and pinion (Z3 = 15 teeth) to mesh with pinich (Z1 = 16 teeth) on the input shaft and gear (Z4 teeth) on the output sahft respectively. It was decided to use a gear ratio of 4 with 3 module in the first stage and 4 module in the second stage.
The centre distance in the second stage is
(a) 90 mm (b) 120 mm
(c) 160 mm (d) 240 mm