A $pn$ junction solar cell of area $1.0\:cm^{2}$, illuminated uniformly with $100\:mW\:cm^{-2}$, has the following parameters: Efficiency $= 15\%$, open circuit voltage $= 0.7\:V$, fill factor $= 0.8$, and thickness $=200 \mu m$. The charge of an electron is $1.6\times 10^{-19}C$. The average optical generation rate (in $cm^{-3} s^{-1}$) is
1. $0.84\times 10^{19}.$
2. $5.57\times 10^{19}.$
3. $1.04\times 10^{19}.$
4. $83.60\times 10^{19}.$