The optional contribution (C (x)) for individuals who provide services is given by (Illustration 1) Find the function () where is the gross income to Optional Contribution.

If the gross is : The contribution will be:

No more than $100,000 6%

In excess of $100,000 but no more than $200,000 10%

In excess of $200,000 but no more than $300,000 13%

In excess of $300,000 but no more than $400,000 15%

In excess of $400,000 but no more than $500,000 17%

In excess of $500,000. 20%