Answer:
b.) stock market prices
Explanation:
The least important factor for determining how big the full monthly mortgage payment will be is - stock market prices.
Current interest rate is the most important factor as the monthly payments are based on the interest rates charged. The higher the rate, the higher the payment.
The down payment size is also important, as the more you pay in down payment, the less will be the loan amount and the monthly payment will also be less.
The local property tax is also a factor that you have to look at when buying a house in a particular state. You will have to pay state taxes also.
Therefore, only the stock market price is the factor that is not important.