how many days does it take a perfect black body cube of 0.01m on a side at 30degree to radiate the same amount of energy that 100watts light bulb uses in one hour​

The answer is 4f======since electrostatic force is given by    we let f be the electrostatic force when  r = 1 m    if we let  denote the electrostatic force when the distance is decreased so that r = 0.5m, then    we established earlier that f = kq₁q₂. therefore    the force will now be 4f.