$A$ solenoid of $1200$ turns is wound uniformly in a single layer on a glass tube $2\,m$ long and $0.2\,m$ in diameter. The magnetic intensity at the center of the solenoid when a current of $2\,A$ flows through it is:

• A
  $2.4 \times 10^3\,A m^{-1}$
• B
  $1.2 \times 10^3\,A m^{-1}$
• C
  $1\,A m^{-1}$
• D
  $2.4 \times 10^{-3}\,A m^{-1}$