In Shubham opinion, his weight is greater than 65 kg but less than 72 kg. His brother does not agree with Shubham and he thinks that Shubham’s weight is greater than 60 kg but less than 70 kg. His mother's view is that his weight cannot be greater than or equal to 68 kg. If all of them are correct in their estimation, what is the average of different probable weights of Shubham ?