A man has $4240,000$ home loan for $20$ years at a nominal rate of $4\mathrm{.}5\%$

convertible monthly. He makes fixed principal repayment of $$1000$ each

month. Find,

a$.$ his loan balance after $12$ years

b$.$ his $100$th month payment

c$.$ the sum of amount of interest paid in the $5$

th year $($from $49$th month to $60$th month$).$