How do I fix this code to get the proper output

This is the code:

amount_borrowed = float(input("Amount borrowed: $"))
interest_rate = float(input("Interest rate: "))
loan_length = int(input("Length of loan (months): "))
i = interest_rate/100
monthly_payment1 = (i / 12) * amount_borrowed    #this is the first part of the payment formula

monthly_payment2 = monthly_payment1 / 1 - (1 + i / 12)**-loan_length          
#second part of monthly payment formula

print("The monthly payment is ${:.2f}" .format(monthly_payment2))

I should get this output:

Amount borrowed: $100.00

Interest rate: 10.0

Length of loan (months): 12

The monthly payment is $8.79.

I keep on getting this:

Amount borrowed: $100

Interest rate: 10

Length of loan (months): 12

The monthly payment is $-0.07