What Is the Radius of a Red Giant Star That $\odot$

Multiple Choice

What is the radius of a red giant star that has a luminosity of 300 L _$\odot$ and a temperature of 4000 K? (Note that the temperature of the Sun is 5800 K.)

A) 8 R _$\odot$
B) 13 R _$\odot$
C) 25 R _$\odot$
D) 36 R _$\odot$
E) 65 R _$\odot$