Answer
Three times the ground state energy.
Work Step by Step
Because of the Pauli exclusion principle, the electrons cannot all be in the same state.
See Figure 41.4.
The ground state can hold 2 electrons (one spin up, one spin down). The first excited state has a degeneracy of 3, and can hold 6 electrons. The second excited state also has a degeneracy of 3, and can hold 6 electrons.
With 10 electrons, two electrons will be in the second excited state, which has energy $3E_{1,1,1}$.
