If $\$ 10,000$ Is Invested For $x$ Years At $5 \%$ Simple Interest, the Total Amount

Essay

If $\$ 10,000$ is invested for $x$ years at $5 \%$ simple interest, the total amount $A$ of the investment is given by the function $$A ( x ) = 500 x + 10,000$$ .(a) Find $A ^ { - 1 }$ .
(b) Find
$A ^ { - 1 } ( 16,500 )$ . What does your answer represent?