Calculate the first-order correction to the energy of a ground-state harmonic oscillator subject to an anharmonic potential of the form ax3 +bx4 where a and b are small (anharmonicity) constants. Consider the three cases in which the anharmonic perturbation is present
(a) during bond expansion (x ≤ 0) and compression (x ≥ 0),
(b) during expansion only,
(c) during compression only.