Refer to the exhibit. What is the OSPF cost to reach the router A LAN 172.16.1.0/24 from B?

The formula used to calculate the OSPF cost is as follows:

Cost = reference bandwidth / interface bandwidth

The default reference bandwidth is 10^8 (100,000,000); therefore, the formula is

Cost = 100,000,000 bps / interface bandwidth in bps

Thus the cost to reach the A LAN 172.16.1.0/24 from B is as follows:
Serial link (1544 Kbps) from B to A cost => 100,000,000 / 1,544,000 = 64
Gigabit Ethernet link on A cost => 100,000,000 / 1,000,000,000 = 1
Total cost to reach 172.16.1.0/24 = 64 + 1 = 65