technically, the 203.250.15.64 would not even get advertised(it is directly connected on a interface that is running RIP), not even 203.250.15.0/24 would get advertised come to think about it. It has been a long time since I have worked with RIP. Also, I believe that RIP advertises exact networks without the subnet mask; example, if RTE had another network connected to it, say 203.250.15.128/30, it would get advertised as a 203.250.15.128 without the subnet mask. When RTC advertises 203.250.15.128 to RTA, it will get inserted into the routing table as 203.250.15.128/26. The /26 on the 203.250.15.128 is coming from what the subnet mask is on the interface of 203.250.15.68/26
Hope this helps
Billy