The following graph shows a proportional relationship. What is the constant of proportionality between y and a in the graph?
Y
8+
6+
2+
2
4
6
8
Constant of proportionality

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?