A Scooty is currently traveling at a speed of (2a – 90) km/hr, and a Bus is moving at a speed of (b + 30) km/hr. If the Scooty's speed were equal to that of the Bus, it would take 2 hours less to cover a distance of 360 km. On the other hand, if the Bus's speed were equal to that of the Scooty, it would take 3 hours more to cover a distance of 540 km. Calculate the difference between the speeds of the Scooty and the Bus.