ID1 = the set of strings beginning with an upper-case letter, followed by any number of lower- case letters or digits. Give parse trees for Sum1 and R. ID2 = the set of strings of letters, digits, underscores and dashes, provided that (1) the first character in the string is an upper-case letter, and (2) the final character is neither an underscore nor a dash. Give parse trees for BB-8 and case_1. ID3 = the set of strings axbx -- any number of a's followed by an equal number of bls. Give parse trees for the empty string (i.e. O a's and O b's) and aabb