Subnetmask for C1 is 255.255.128.0. So, we can network ID reserved first 17 bits as it it classless.
Similarly, for C2 255.255.192.0. network ID reserved first 18 bits.
for C1: 203.197.2.53 AND 255.255.128.0 = 203.197.0.0 /17
for C2: 203.197.75.201 AND 255.255.192.0 = 203.197.65.0/18
as C2 has reserved 1 extra bit for subnet ID,
C1 assume the C2 is inside its network.
so,
C1 assumes C2 is on same network, but C2 assumes C1 is on a different network