In the figure shown, PQRSTU is a regular polygon with sides of length x. What is the perimeter of triangle PRT in terms of x ?

~$x\sqrt{3} \over 2$~

x~$\sqrt{3}$~

~$3x\sqrt{3}\over 2$~

3x~$\sqrt{3}$~

4x~$\sqrt{3}$~