If money is worth $16\%$ simple interest, find the values of debt of $K15,000$ due in $9$ months with interest at $11\mathrm{.}5\%$

$($a$)$ today

$($b$)4$ months from now

$($c$)1$ year from now.

Debts of $K4,500$ due $20$ days ago and $K7,000$ due in $50$ days are to be settled by a payment of $K900$ now and a final payment $90$ days from now. Find the value of the final payment at a simple interest rate of $12\%$ with a focal date at the present.