Financial quantities in American notation. These have a leading dollar sign $($$$),$ an optional string of asterisks $(*$used on checks to discour$-$ age fraud$),$ a string of decimal digits, and an optional fractional part consisting of a decimal point $(.)$ and two decimal digits. The string of digits to the left of the decimal point may consist of a single zero $(0).$ Otherwise it must not start with a zero. If there are more than three digits to the left of the decimal point, groups of three $($counting from the right$)$ must be separated by commas $(,).$ Example: $$**2,345\mathrm{.}67.($Feel free to use $$productions$$ to define abbreviations, so long as the language remains regular.$)$