A Giant Star Radiates Energy at the Rate Of $3.0 \times 10 ^ { 30 } \mathrm {~W}$

A giant star radiates energy at the rate of $3.0 \times 10 ^ { 30 } \mathrm {~W}$ and its surface temperature has been measured to be 3000 K. Assuming that it is a perfect emitter, what is the radius of this star? $( \sigma =$ $\left. 5.67 \times 10 ^ { - 8 } \mathrm {~W} / \mathrm { m } ^ { 2 } \cdot \mathrm { K } ^ { 4 } \right)$

A) $7.8 \times 10 ^ { 10 } \mathrm {~m}$
B) $1.9 \times 10 ^ { 11 } \mathrm {~m}$
C) $2.3 \times 10 ^ { 11 } \mathrm {~m}$
D) $1.4 \times 10 ^ { 10 } \mathrm {~m}$
E) $8.7 \times 10 ^ { 10 } \mathrm {~m}$