A retaining wall of height $10 \text{ m}$ with clay backfill is shown in the figure (not to scale). Weight of the retaining wall is $\text{5000 kN per m}$ acting at $3.3 \text{ m}$ from the toe of the retaining wall. The interface friction angle between base of the retaining wall and the base soil is $20^\circ$. The depth of clay in front of the retaining wall is $2.0\text{ m}$. The properties of the clay backfill and the clay placed in front of the retaining wall are the same. Assume that the tension crack is filled with water. Use Rankine's earth pressure theory. Take unit weight of water, $\gamma _{w}=9.81\text{kN/m}^3$.
The factor of safety (round off to two decimal places) against sliding failure of the retaining wall after ignoring the passive earth pressure will be ___________________________