Identify the current expression for Kutzbach's criterion of mobility, given n is the number of links, j1 is the number of low-pair joints and j2 is the number of high-pair joints.
1
m = 2 (n - 1) - j1 - j2
2
m = 3 (n - 1) - j1 - 2j2
3
m = 3 (n - 1) - 2j1 - j2
4
m = 3 (n - 1) + j1 - j2