Let a, b, c, and d be real numbers with |a-b|=2,|b-c|=3, and |c-d|=4. What is the sum of all possible values of |a-d| ?

**Answer Choices**

A. 9

B. 12

C. 15

D. 18

E. 24

Let a, b, c, and d be real numbers with |a-b|=2,|b-c|=3, and |c-d|=4. What is the sum of all possible values of |a-d| ?

**Answer Choices**

A. 9

B. 12

C. 15

D. 18

E. 24