Stuck on problem set 1 part c: bi-section search for paying off credit card in 12 months.
The program seems to be running properly with the high and low values changing according to the previous results and being averaged before a new iteration, but the payments are never high enough to pay off the debt.
The equation I'm using to define the high end of my search parameters is the one provided in the problem set,

i.e. high = (balance * (1 + (interestRate /12))**12) / 12

but even if I take the result of this as the monthly payment it never pays off the debt with a high interest rate.

Question

Stuck on problem set 1 part c: bi-section search for paying off credit card in 12 months. 
The program seems to be running properly with the high and low values changing according to the previous results and being averaged before a new iteration, but the payments are never high enough to pay off the debt.
The equation I'm using to define the high end of my search parameters is the one provided in the problem set, 

i.e. high = (balance * (1 + (interestRate /12))**12) / 12

but even if I take the result of this as the monthly payment it never pays off the debt with a high interest rate.