its the the first one u said
Given that,
Energy 
Surface temperature = 11000 K
Emissivity e =1
(a). We need to calculate the radius of the star
Using formula of energy



Put the value into the formula


(b). Given that,
Radiates energy 
Temperature T = 10000 K
We need to calculate the radius of the star
Using formula of radius

Put the value into the formula


Hence, (a). The radius of the star is 
(b). The radius of the star is 
Answer:
23.3 g/cm3
Explanation:
First of all, this should be in the math section. I just so happen to also be good at math. Cheers!