Martin is looking out of the window and sees a flying plane. He wonders, how fast the plane could be flying. In his mind, Martin counts that the plane was in his field of view between two houses for 10 seconds (the aircraft is in the field of view if Martin can see at least half of the aircraft). According to the rule "1 thumb in the distance of an outstretched hand corresponds to 2.5 angular degrees" he calculates that the plane has flown 7.5 of his "thumbs" during that time. Martin doesn't know how far the plane was flying, but he makes an estimation, that in his field of view, it occupied about half of his thumb during the whole observation and that the plane could be a Boeing 737-800. Calculate, how fast the plane was flying, based on Martin's estimations.