A Conducting Rod Is Free to Slide on Horizontal, Frictionless $2.0 \mathrm{~m}$

A conducting rod is free to slide on horizontal, frictionless rails separated by $2.0 \mathrm{~m}$ . At a particular time, the rod is sliding at $4.0 \mathrm{~m} / \mathrm{s}$ to the right, as shown. A uniform magnetic field is directed into the page. If a current of $40 \mathrm{~mA}$ is generated in the circuit at this time, and the resistance $\mathrm{R}$ is $0.36 \Omega$ , what is the magnitude of the magnetic field between the rails?

A) $0.028 \mathrm{~T}$
B) $1.8 \mathrm{mT}$
C) $0.11 \mathrm{~T}$
D) $3.6 \mathrm{mT}$
E) $14 \mathrm{mT}$