C$++$ Define a function FindEmployeeTax$()$ that takes one integer parameter as a person's age, and returns the person's tax percent as a double. The tax percent is returned as follows:

If the person's age is less than $20$ years old, then the tax percent is $0\mathrm{.}39.$

If the person's age is between $20$ and $60$ years old inclusive, then the tax percent is $0\mathrm{.}24.$

Otherwise, the tax percent is $0\mathrm{.}13.$

Ex: If the input is $15,$ then the output is:

$0\mathrm{.}39$