John took out a $$2,000,000$ construction loan, disbursed to him in three installments. The first installment of $$1,000,000$ is disbursed immediately and this

followed by two $$500,000$ installments at six$-$month intervals. The interest on the

loan is calculated at a rate of $15\%$ convertible semiannually and accumulated to

the end of the second year. At that time, the loan and accumulated interest will

be replaced by a $30-$year mortgage at $12\%$ convertible monthly. The amount of the

monthly mortgage payment for the first five years will be one$-$half of the payment

for the sixth and later years. The first monthly mortgage payment is due exactly

two years after the initial disbursement of the construction loan. Calculate the

amount of the twelfth mortgage payment.