The physics of a lightbulb filament?

The filament in an incandescent bulb is made from tungsten. The resistivity of tungsten is 5.6 x 10-8 Ωm. The radius of the tungsten wire is 0.045 mm. If the bulb is to be plugged into a 120-V outlet and is to draw a current of 1.24 A, how long must the wire be? In doing this question be sure to derive an algebraic expression for the length of the wire, L , in terms of the voltage, V , the current, I , the radius of the wire, r , and the resistivity of the wire, ρ , before substituting the numerical values.