Given: A type UF cable is run to a residential lamp post light that is fed from a 120 volt, 15 amp-GFCI protected branch circuit. The cable is buried in earth without additional physical protection. What is the minimum allowable burial depth?

Given: A type UF cable is run to a residential lamp post light that is fed from a 120 volt, 15 amp-GFCI protected branch circuit. The cable is buried in earth without additional physical protection. What is the minimum allowable burial depth?