Answer: 61.1 is the answer I wish this answer help you.
The answer is C
The colour that you see is what is being reflected and the colour that you don't see is what is being absorbed. In this case, you don't see any colour, so all wavelengths are being absorbed.
I'm pretty sure that you put incorrect temperature number, since the number of temperature that you currently given does not make any sense.
Insert your correct temperature in this equation :
Ek = (3/2)kT
Hope this helped you out
