An Ideal Solenoid Having a Coil Density of 5000 Turns $10 \mathrm {~cm}$

An ideal solenoid having a coil density of 5000 turns per meter is $10 \mathrm {~cm}$ long and carries a current of $4.0 \mathrm {~A}$ . What is the strength of the magnetic field at its center?

A) $6.2 \mathrm { mT }$
B) $3.1 \mathrm { mT }$
C) $13 \mathrm { mT }$
D) $25 \mathrm { mT }$