How to calculate "cost" in OSPF?

Network Layout / OSPF 1

R1#show ip route OSPF

       10.0.0.0/24 is subnetted, 3 subnets

O       10.1.23.0 [110/65] via 10.1.12.2, 00:03:01, Serial0/0

O       10.1.34.0 [110/129] via 10.1.12.2, 00:03:01, Serial0/0

110  = OSPF's Administrative Distance

  65 = Cost from 10.1.12.0 to 10.1.23.0 (Serial + Fast Ethernet)

129 = Cost from 10.1.12.0 to 10.1.34.0 (Serial + Fast Ethernet + Serial)

R1#show ip OSPF interface

Serial0/0 is up, line protocol is up

  Internet Address 10.1.12.1/24, Area 0

  Process ID 1, Router ID 10.1.12.1, Network Type POINT_TO_POINT, Cost: 64

Serial = Cost 64

FastEthernet1/0 is up, line protocol is up

  Internet Address 10.1.23.1/24, Area 0

  Process ID 1, Router ID 10.1.23.1, Network Type BROADCAST, Cost: 1

FastEthernet = Cost 1