A Slice of Pizza, in the Form of a Sector $\theta$

Essay

A slice of pizza, in the form of a sector of a circle, is to have a perimeter of 14 inches. What should be the radius of the pan to make the slice of pizza largest.
(The area of a sector of a circle, where $\theta$ is the central angle in radians and the arc length along a circle is S = r $\theta$ with $\theta$ in radians.)