[PV of ordinary annuity 20 per., 8% (9.81815) –
PV of ordinary annuity 10 per., 8% (6.71008)]
PV of next 10 years of maintenance
[(PV of ordinary annuity 30 per., 8% (11.25778) –
PV of ordinary annuity 20 per., 8% (9.81815)]
PV of last 10 years of maintenance