Study Question - Real Battery with bulb, current/resistance

[exitwound]

Homework Statement

Homework Equations

$KE = 1/2mv^2$
$F_B=I(L x B)$

The Attempt at a Solution

I have the answer to this, (D) but I don't know how to get it.

I know that the gained kinetic energy is equal to the lost potential energy of the system. What's the potential energy of the system? ILB? If so, how does that translate to answer D?

 

[Delphi51]

You can find the force on the rod using F = ILB. Use accelerated motion formulas to find the speed after time t.