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 spots a very distant object O in line with AC. He then walks perpendicular to AC, up to B, a distance of 100 m, and looks at O and C again. Since O is very distant, the direction BO is practically the same as AO ; but he finds the line of sight of C shifted from the original line of sight by an angle $ \theta$ = $40^{\circ}$ ($ \theta$ is known as 'parallax'). Estimate the distance of the tower C from his original position A.