Spell out percentages under 10 or express as numerals?

Which is correct?
The federal government established a goal of contracting with women-owned small businesses for ________ of the total.
a. five percent
b. 5 percent
c. 5%

Explanation:
According to AP style, percentages are an exception to the rule requiring numbers under 10 to be spelled out. Percent is spelled out, however, rather than symbolized.

And the only exception to that rule is if a percentage starts the sentence. We’d say, for example, that “Five percent of the federal government’s contracts are issued to women-owned small businesses.” Don’t quote that statistic, though — apparently that’s an as-yet unreached goal.

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