annualInterestRate=.2
balance=320000
monthlyInterestrate=annualInterestRate/12
balance_initial=balance
lowerbound=(1/12)*balance
upperbound=balance*(1+monthlyInterestrate)**(12)/12
monthlyPayment=(upperbound+lowerbound)/2
while balance>-.00001 and balance<.00001:
for i in range(12):
    balance=balance-monthlyPayment + (balance-monthlyPayment)*monthlyInterestrate
if balance>0:
    lowerbound=monthlyPayment
if balance<0:
    upperbound=monthlyPayment

print('Lowest Payment: ' + str(round(monthlyPayment, 2)))