First, we need to know the total price of the house. Then, we can calculate the loan amount according to the down payment ratio and the loan period. Finally, the monthly payment can be calculated according to the loan amount and term.

Total known house price: 6,543,800+0.8 million.

It is known that the down payment ratio is 50%, that is, the down payment amount is: total price × down payment ratio =180× 0.5 = 900,000.

According to the loan amount = total price-down payment amount, we can calculate the loan amount:180× (1-0.5) = 900,000.

Known loan term: 12 months.

The known monthly interest rate is 0.005.

According to the repayment method of equal principal and interest, the calculation formula of monthly payment is:

Monthly payment = [loan principal x monthly interest rate x (1+ monthly interest rate) loan periods ]/[( 1+ monthly interest rate) loan periods-1]

Substituting the data into the formula, the monthly supply is 77500 yuan.

Therefore, a house with a down payment of 50% 654.38+0.8 million yuan has a monthly payment of 77,500 yuan.