Usha swims in a 90 m long pool. She covers 180 m in one minute by swimming from one end to the other and back along the same straight path. The average speed and average velocity of Usha respectively is
1. 18 m/s and 18 m/s
2. 1.8 m/s and 0 m/s
3. 3 m/s and 3 m/s
4. 3 m/s and 0 m/s