Counting Occurrences Using Regular Expressions Let ={a,b} Write a regular expression that generates precisely those words over that contain at most 1 non-overlapping occurrences of the (contiguous) subword aab. Examples: - babab contains 1 non-overlapping occurrences of bab: babab or babab - bababab contains 2 non-overlapping occurrences of bab: bababab The regular expressions have the following syntax: - for union, for concatenation and for Kleene star - or for , the language containing only the empty word - 0 (zero) for , the empty language - can often be left out Example expression: abcd(a+L+Obc)c is short for abcd(a++bc)c