A train goes from P to Q at a speed of 20 km/h. Then it goes from Q to R at a speed of q km/h. Finally the train goes from R to S at a speed of r km/h. The distances from P to Q, Q to R and R to S are equal. If the average speed from P to R is \(\frac{280}{11}\) km/h, and the average speed from Q to S is \(\frac{112}{3}\) km/h, then what is the value of r ?