To find out how much Mark still owes on his debt, we need to calculate the amount of interest that has accrued on the loan over the time that he has been paying it off. The interest on the loan is compounded semi-annually, so the amount of interest that accrues on the loan will be added to the principal every six months. Since Mark has been paying off his debt for 8 years and the interest is compounded semi-annually, he will have made 16 payments of $500.
To calculate the total amount of interest that has accrued on the loan, we need to know the original principal amount of the loan. Since we don't have that information, we won't be able to calculate the exact amount that Mark still owes on his debt. However, we can use the information that we have to make an educated guess.
If Mark has been making payments of $500 every six months for eight years, then he has paid a total of $500 x 16 = $<<50016=8000>>8000 in principal and interest payments. If the interest on the loan is 2% compounded semi-annually, then the total amount of interest that has accrued on the loan over the past eight years is $8000 x 2% = $<<80002*.01=160>>160. This means that the original principal amount of the loan was $8000 - $160 = $<<8000-160=7840>>7840.
Since Mark still has 8 years left to pay off the debt, and he is making payments of $500 every six months, he will need to make a total of 8 years x 2 payments per year = <<82=16>>16 more payments of $500 to pay off the debt. This means that he will have to pay a total of $500 x 16 = $<<50016=8000>>8000 in principal and interest over the next eight years.
Since the total amount of interest that has accrued on the loan over the past eight years was $160, the total amount of interest that will accrue on the loan over the next eight years is also $160. This means that the total amount of interest that Mark will have to pay over the next eight years is $160 x 2 = $<<160*2=320>>320.
Adding the amount of interest that Mark will have to pay over the next eight years to the amount of principal that he will have to pay, we find that the total amount that Mark will owe on the loan over the next eight years is $8000 + $320 = $<<8000+320=8320>>8320.
Therefore, if Mark has been paying off his debt for eight years and still has eight years left to pay, he still owes a total of $8320 on the loan.