Three sprinters A, B and C had to sprint from points P to Q and backagain (starting in that order). The time interval between their staring timesof the three sprinters was 5 seconds each. Thus C started 10 seconds after A,while B started 5 seconds after A. The three sprinters passed a certain pointR, which is somewhere between P and Q, simultaneously (none of them havingreached Q yet). Having reached Q and reversed the direction, the thirdsprinter met the second one 9 m short of Q and met the first sprinter 15 mshort of Q. Find the speed of the first sprinter if the distance between PQ isequal to 55 m?