Describe, using a regular expression, the language which has (4 x 1 = 4 points)

1. only those strings over A= {0, 1} which have at least one zero at the end
2. only those strings over A= {0, 1} which have at least one zero
3. only the string 001100
4. only those strings over A= {0, 1} that contain at least 2 zeros