In this class we will talk about alphabets A and languages L. An alphabets A is any non-empty finite set. We let A* be the set of all finite strings of elements from A. So A* is infinite. Languages are sets whose elements come from some A , so they are subsets of A .

Consider the language L = { x | x is a binary string starting with 11 and ending with a 1 followed by an even number of 0s} = { x | x = 11y10t where y {0, 1} and t 2 is even }.

1). What is the alphabet of L ? (This answer is not unique.)

2). Give an example of a subset B of L with |B| = 5.