A vertical smooth rigid retaining wall is supporting horizontal ground with dry cohesionless backfill having a friction angle of $30^{\circ}$. The inclinations of failure planes with respect to the major principal plane for Rankine's active and passive earth pressure conditions, respectively, are
- $30^{\circ}$ and $30^{\circ}$
- $60^{\circ}$ and $60^{\circ}$
- $30^{\circ}$ and $60^{\circ}$
- $60^{\circ}$ and $30^{\circ}$