Construct the call graph for a set of seven telephone numbers 555-0011, 555-1221, 555-1333, 555-8888, 555-2222, 555-0091, and 555-1200 if there were three calls from 555-0011 to 555-8888 and two calls from 555-8888 to 555-0011, two calls from 555-2222 to 555-0091, two calls from 555-1221 to each of the other numbers, and one call from 555-1333 to each of 555-0011, 555- 1221, and 555-1200.

At the tops of our directed graph will be telephone numbers. Since there are 7 phone numbers, then there will be seven vertices. Since all numbers are 555, for convenience, only the last four digits will be in the vertices.

We will present all the information in the form of a list, so that it is convenient to perceive it.

1) From 0011 to 8888 – 3 calls ( 3 arrows );

2) From 8888 to 0011 – 2 calls ( 2 arrows );

3) From 2222 to 0091 – 2 calls ( 2 arrows );

4) From 1221 to other numbers – 2 calls ( 2 arrows );

5) From 1333 to 0011, 1221, 1200 – 1 calls ( 1 arrows )