Triangle A B C has a right angle at B. Point D is the foot of the altitude from B, A D=3, and D C=4. What is the area of \triangle A B C ?

**Answer Choices**

A. 4 \sqrt{3}

B. 7 \sqrt{3}

C. 21

D. 14 \sqrt{3}

E. 42

Triangle A B C has a right angle at B. Point D is the foot of the altitude from B, A D=3, and D C=4. What is the area of \triangle A B C ?

**Answer Choices**

A. 4 \sqrt{3}

B. 7 \sqrt{3}

C. 21

D. 14 \sqrt{3}

E. 42