Final answer:
Nancy would owe penalty fees of $200 for paying her mortgage loan early.
Step-by-step explanation:
To calculate the penalty fees that Nancy would owe for paying her mortgage loan early, we first need to find the amount of interest paid within six months. Since the interest rate is 6% annually, the monthly interest rate is 6% / 12 = 0.5%. The interest paid within six months is 0.5% * $50,000 = $250.
The lender charges 80% of six months' interest as a pre-payment fee. Therefore, Nancy would owe penalty fees of 80% * $250 = $200.