Consider the following processes for the manufacture of gears
1. Casting
2. Powder metallurgy
3. Machining from bar stock
4. Closed die forging
The correct sequence in increasing order of bending strength of gear teeth is
(a) 1,2,3,4 (b) 1,2,4,3
(c) 2,1,4,3 (d) 2,1,3,4