Please answer the following questions.

1		A system is composed of three components. All three must function in order for the system to work. Each one has a reliability of .90. System reliability is:
			A)	.729
			B)	.900
			C)	.990
			D)	.999
			E)	2.700.
2		A system is composed of three components, I, II, III. The reliabilities of the three components are respectively 0.50, 0.90, and 0.90. III is a standby for II that switches on only if II fails. The overall system reliability is:
			A)	2.300
			B)	.405
			C)	.495
			D)	.860
			E)	.540
3		A machine can operate for an average of 99 hours before needing service. Service time averages one hour. The availability of the machine is:
			A)	1.00
			B)	.99
			C)	.98
			D)	.97
			E)	none of these.
4		If the MTBF increases and the expected repair time remains the same, availability will:
			A)	decrease
			B)	remain the same
			C)	increase
			D)	impossible to say
5		Which of the following statements about a redundant component is false?
			A)	It is a backup.
			B)	It might not be used.
			C)	It increases the reliability of the system.
			D)	It decreases the MTBF.
			E)	It decreases the failure rate.