In Figures (a) and (b), two air-cored solenoids P and Q have been shown. They are placed near each other. In Figure (a), when I_P, the current in P, changes at the rate of 5 A s^-1 , an emf of 2 mV is induced in Q. The current in P is then switched off, and the current changing at  2A s^-1 is fed through Q as shown in the figure. What emf will be induced in P?

• A

  $8\times {10}^{-4}\mathrm{V}$

• B

  $2\times {10}^{-3}\mathrm{V}$

• C

  $5\times {10}^{-3}\mathrm{V}$

• D

  $8\times {10}^{-2}\mathrm{V}$