Hydrology and Runoff

In Snyder's synthetic unit hydrograph, main stream length $L = 20\text{ km}$ and centroid distance $L_c = 10\text{ km}$ (so $L \cdot L_c = 200\text{ km}^2$). Given $200^{0.3} \approx 4.90$ and regional coefficient $C_t = 1.5$, basin lag $t_p = C_t (L L_c)^{0.3}$ in hours is (rounded off to one decimal place):