Consider the following statements with reference to the equation $$\nabla.\overrightarrow J=-\frac{\partial\rho}{\partial t}$$

1. This is a point from the continuity equation
2. Divergence of current density is equal to the decrease of charge per unit volume per unit time at every point.
3. This is Maxwell's divergence equation
4. This represents the conservation of charge.

Select the correct answer.

The velocity of propagation of electromagnetic wave 'n' an underground cable with relative permittivity of 3 will be ________m/sec