Need help on this problem about Theory of Computation:

2. Give a regular expression for a certain type of notation for real numbers on which all of the following rules hold. Let -(0, 1, 2, 3, 4, 5, 6, 7, 8, 94", -',x) (a) The number can be preceded by a +orsign or the sign may be absent. (b) Numeric values must be of the form cbP2 . . . bn, where bi is any digit, but c must be ign or the sign mav be absent. nonzero (c) The number may be folowed by an exponent field of the form e +" yy or e." yy, where y can be any digit