Correct Answer - Option 3 : m = 3 (n - 1) - 2j

_{1} - j

_{2}
**Explanation:**

Degree of freedom(DOF)/Mobility of linkage –

- Degree of freedom of plane mechanism is defined as the number of inputs or independent coordinates needed to define the configuration or
- position of all the links of mechanism with respect to a fixed link.

Kutzback equation of degree of freedom,

**F = 3 × (n – 1) – 2j**_{1} – j_{2}

Where, n = number of links in the mechanism, j_{1} = Binary joint or lower pair, j2 = higher Pair and F = Degree of freedom

Grubler's criterial applies to planar mechanism having no higher pairs (h = 0) and completely constraint (F = 1).

1 = 3 × (n – 1) – 2j

∴ 1 = 3n – 3 – 2j

∴ 2j – 3n + 4 = 0