Let the line of 14 be AB and its'mid point( where the is a perpendicular line = C )
Also let centre of circle be O
So AC= (14/2) = 7 unit
RECALL : X is the radius and radius of circle is constant
Using pytagoras theorem:
[ AX^2 = XO^2 + OA^2 ]
You'll get ... (7)^2 + (4)^2 = 65
So AX^2 = 65
And AX = square root of 65 ... = 8.06
This approcimately 8.1
Therefore the answer is A
Hope u understood