Circles with centers P, Q, and R, having radii 1,2 , and 3 , respectively, lie on the same side of line l and are tangent to l at P^{\prime}, Q^{\prime}, and R^{\prime}, respectively, with Q^{\prime} between P^{\prime} and R^{\prime}. The circle with center Q is externally tangent to each of the other two circles. What is the area of \triangle P Q R ?
Answer Choices
A. 0
B. \sqrt{\dfrac{2}{3}}
C. 1
D. \sqrt{6}-\sqrt{2}
E. \sqrt{\dfrac{3}{2}}