A man has RM$240,000$ home loan for $20$ years at a nominal rate of $4\mathrm{.}5\%$

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

month. Find,

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$).$