A man wishes to estimate the distance of a nearby tower from him. He stands at a point A in front of the tower C and sports a very distant object O in line with AC. He then walks perpendicular to AC up to B , a distance of 100m , and looks at O and C again. Since O is very distant, the direction BO is practically the same as a AO; but he finds the line of sight of C shift from the original line of sight by an angle θ = 40 ̊ ( θ is known as “parallax” ), estimate the distance of the tower C from his original position A.