The drainage are of a watershed is $50 \: km^2$. The $\phi$ index is $0.5$  cm/hour and the base flow at the outlet is $10 \: m^3/s$. One hour unit hydrograph (unit depth $=1 \: cm$) of the water shed is triangular in shape with a time base of $15$ hours. The peak ordinate occurs at $5$ hours.

The peak ordinate (in $m^3/s/cm$) of the unit hydrograph is

1. $10.00$
2. $18.52$
3. $37.03$
4. $185.20$