The trial wave function of a system is expanded as $\psi_t = c_1\phi_1 + c_2\phi_2$. The matrix elements of the Hamiltonian are $\langle\phi_1|\hat{H}|\phi_1\rangle = 0$; $\langle\phi_1|\hat{H}|\phi_2\rangle = 2.0 = \langle\phi_2|\hat{H}|\phi_1\rangle$ and $\langle\phi_2|\hat{H}|\phi_2\rangle = 3.0$. The approximate ground-state energy of the system from the linear variational principle is