balance = 320000
annualInterestRate = 0.2

_balance = balance
interest = 0.0
lower = balance/12
upper = (balance*(1+annualInterestRate/12)**12)/12
payment = round((lower+upper)/2,2)
while True:
    balance = _balance
    mes = 1
    while mes < 13:
        interest = (balance - payment)*(annualInterestRate/12)
        balance = balance - payment + interest
        mes += 1
    if (upper-lower) <= 0.1:
        break
    elif balance > 0:
        lower = payment
        payment = round((payment+upper)/2,2)
    else:
        upper = payment
        payment = round((payment+lower)/2,2)
print('Lowest Payment: ' + str(round(payment,2)) )