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6. Use regular expression (in the form of production rules) to specify the syntax (a) natural numbers. (b) all strings over alphabet (a, b, A, B} that starts with capital letters. (c) Numeric constants in a language X. A numeric constant is an octal, decimal, or hexadecimal integer. An octal integer begins with 0, and may contain only the digits from 0 to 7. A hexadecimal integer begins with Ox or ox, and may contain the digits from 0 to 9 and letters from a/A to f/F. Decimal integers are those we normally use in our daily life