Union and intersection

Question

A and B are sets of real numbers defined as follows. Write 4 cap B A cup B using interval notation. If the set is empty, write empty set .

A={ z|z<4}

B={ z|z>=7} (or equal to)

Answer 1

A intersection B is the null set. There are no elements of A that overlap elements of B

A Union B is the interval (-infinity, 4) U [7, infinity)