Need geometry now will medal and make brainliest ab is tangent to circle o at b. if ab=7, and ao = 17.4 what is the length of the radius (r)? \ diagram attached explain too : )

On Monday at 1 p.m., when the ocean's surface was at an elevation of 2.2 feet, Winston went to a surf shop that was 8.2 feet above the ocean's surface. At 7 p.m. when the ocean's surface was at an elevation of -2.4 feet, Winston ate dinner at a restaurant whose deck was 10 feet above the ocean's surface.