What equal series of payments must be paid into a sinking fund in order to accumulate each given$$ amount?

$($a$)$ $$15$ comma $000$ in $9$ years at $8\%$ compounded semiannually when payments are semiannual.

$($b$)$ $$2$ comma $000$ in $16$ years at $6\%$ compounded quarterly when payments are quarterly.

$($c$)$ $$38$ comma $000$ in four years at $7\mathrm{.}35\%$ compounded monthly when payments are monthly.