8 7
6
> 2
{} } }
-9-8-7-6-5 -4 -3 -2
+
1 2 3 4 5 6 7 8 9
2+
-3+
-4+
45+
-6+
-7+
-8+
-9

Aparticular telephone number is used to receive both voice calls and fax messages. suppose that 25% of the incoming calls involve fax messages, and consider a sample of 25 incoming calls. (a) what is the expected number of calls among the 25 that involve a fax message?