A loan of $80,000$ is repayable over $25$ years by level monthly instalments in arrears of capital and interest. The repayments are calculated using an effective rate of interest of $8\%$ per annum. Calculate:

a$)$ The capital repaid in the first monthly instalment.

b$)$ The total amount of interest paid during the last six years of the loan.

c$)$ The interest included in the final monthly payment.

d$)$ Explain how your answer to b$)$ would alter if$,$ under the original terms of the loan, repayments had been made less frequently than monthly.