In a six-node network, two nodes are connected to all the other nodes. Of the remaining four, each is connected to four nodes. What is the total number of links in the network?

- 7
- 13
- 15
- 26

**Answer**

Let A, B, C, D, E, and F be the six nodes.

A and B are connected to all other nodes. In this case, C, D , E and F gets 2 links each. Since these four nodes are connected to total four nodes, they will make two more nodes.

Links - AB, AC, AD, AE, AF, BC, BD, BE, BF, EF, EC, DF, DC

Total number of links in the network is 13.

**The correct option is B.**