The measure of ∠ROU is 94°. That is a central angle, which means that the arc it intercepts also measures 94°. Because ∠SOT is vertical to ∠ROU it is also a 94° angle with a 94° intercepted arc. The other 2 angles, ∠SOR and ∠TOU are vertical and have the same measure, both the angles and their intercepted arcs. Those measures will split the difference of 360-94-94, which is 172. 172/2 is 86. That means that those arcs also measure 86. Arc SRT is the addition of arc SR, RU. and UT, which are 86+94+86, respectively, which add up to 266. Second choice down.
