In a 400 metres race, A gives B start of 5 seconds and beats him by 15m. In another race of 400 metres, A beats B by 50/7 seconds, find their speeds.

1) 8 m/s ; 7 m/s
2) 7 m/s ; 5 m/s
3) 5 m/s ;3 m/s
4) none of these