Two Cylindrical Steel Rods a and B Have Radii of 0.02

Two cylindrical steel rods A and B have radii of 0.02 m and 0.04 m,respectively.The two steel rods conduct the same amount of heat per unit time for the same temperature differences between their two ends.What is the ratio of the lengths of the rods,L_A/L_B?

A) 0.25
B) 0.50
C) 1.00
D) 2.00
E) 4.00