In the following, a number-string is a non-empty sequence of decimal digits, i.e., something in the language defined by the regular expression [0-9] +. The value of a number-string is the usual...

In the following, a number-string is a non-empty sequence of decimal

digits, i.e., something in the language defined by the regular expression [0-9]

+. The

value of a number-string is the usual interpretation of a number-string as an integer

number. Note that leading zeroes are allowed.

Make for each of the following languages a regular expression that describes that

language.

a) All number-strings that have the value 42.

b) All number-strings that do not have the value 42.

c) All number-strings that have a value that is strictly greater than 42.