A ring of mass 4 kg is uniformly charged with  $\text{λ = 4\hspace{0.17em}}C{\text{m}}^{\text{-1}}$ and kept on rough horizontal Surface with  friction Coefficient $\text{μ=}\frac{\text{π}}{\text{4}}\text{.}$ A time varying magnetic    field ${\text{B = B}}_{\text{0}}{\text{t}}^{\text{2}}$ is applied in  a  circular region of radius  $\text{a}\left(\text{a < r}\right)$ perpendicular to the plane of ring as shown in figure.

Find out the time(in seconds)  when ring just starts to rotate on  surface. $\left(\text{Take a = 5cm and\hspace{0.17em}\hspace{0.17em}}g{\text{=10ms}}^{\text{-2}}\right){\text{B}}_{\text{0}}\text{=125}$ SI unit.