A technician services machines of companies operating in the Phoenix area. Depending on the type of malfunction, the service call can take exactly 1, 2, 3, or 4 hours. The different types of malfunctions occur at the same frequency.

Duration of Call (x)	f(x)
1	0.25
2	0.25
3	0.25
4	0.25

What is the probability that a service call will take less than three hours?

	a.	0.25
	b.	0.75
	c.	1.00
	d.	0.50