Hydrology and Runoff

In Philip's infiltration equation $I = S t^{1/2} + A t$, sorptivity $S = 20\text{ mm/h}^{1/2}$ and $A = 5\text{ mm/h}$. After $t = 4\text{ hours}$ ($t^{1/2} = 2.0$), the cumulative infiltration $I = 20(2.0) + 5(4)$ in mm is: