Another running club, Choco, designed a different training programme. The runners in Choco began with running 400 m on the 1 session. On each subsequent session, the distance covered was increased by 10% of the distance covered on the previous session. From the 11th session onwards and for all subsequent sessions, the distance covered was increased by r% of the distance covered on the previous session. (iv) Given that the runners from Choco club covered at least 20 km on the 20th training session, find the range of values of r.