Let U = {0, 1, 2, 3, 4, 5, 6 $$\left| B ^ { \prime } \right|$$

Let U = {0, 1, 2, 3, 4, 5, 6, 7, A, B}
A = {0, 5, 6, B}
B = {1, 5, 7, A}
Find the following:
- $$\left| B ^ { \prime } \right|$$