An embankment is to be constructed with a granular soil (bulk unit weight $=20 \: kN/m^3$) on a saturated clayey silt deposit (undrained shear strength $=25$ kPa). Assuming undrained general shear failure and bearing capacity factor of $5.7$, the maximum height (in m) of the embankment at the point of failure is

1. $7.1$
2. $5.0$
3. $4.5$
4. $2.5$