I need a answer 4.71 x 0.2

ASAP

When y’all answer can y’all explain too !

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate.in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle