In the diagram, AB is 6 units, BC is 30 units, and AE is 4 units.
Triangle A C D is shown. Line segment B E is drawn from side C A to side D A to form triangle A B E. The length of C B is 30, the length of B A is 6, and the length of A E is 4.
If by the SAS similarity theorem, what is AD?
16 units
20 units
24 units
28 units