There are $50$ turns of a wire in every $1$ $cm$ length of a long solenoid. If $4$ $A$ current is flowing in the solenoid,the approximate value of the magnetic field along its axis at an internal point and at one end will be respectively:

• A
  $12.6 \times 10^{-3} \, Wb/m^2, \; 6.3 \times 10^{-3} \, Wb/m^2$
• B
  $12.6 \times 10^{-3} \, Wb/m^2, \; 25.1 \times 10^{-3} \, Wb/m^2$
• C
  $25.1 \times 10^{-3} \, Wb/m^2, \; 12.6 \times 10^{-3} \, Wb/m^2$
• D
  $25.1 \times 10^{-5} \, Wb/m^2, \; 12.6 \times 10^{-5} \, Wb/m^2$