Astrophysics: radiation pressue&gas pressure

[nbky]

first sorry for my english.

i wrote the problem and equations.the result is:

critical mass of a star =2,5x mass of the sun.

but i couldn't find the result.pls help me to find the result with this equations.

 

[nbky]

i solved the problem.

tempeture of radiation and tempeture of gas are equal.And when i add a equation on the problem which is P=GM^2/R^4, i solve the problem.