The Functioning of a Particular Machine Is Dependent on Two

Multiple Choice

The functioning of a particular machine is dependent on two safety valves: A and B. In order for the machine to operate perfectly BOTH valves must function well. The valves have been known to fail when subjected to extremely stressful conditions such as extreme heat or cold. Valve A has a 10% chance of failure while valve B has a 5% chance of failure under similar stress such as extreme heat or cold. If you are in charge of maintaining this machine, then you can say that there is at worst a _____ chance of this machine breaking down and so with _____ chance the machine will work fine.

A) 10%; 90%.
B) 15%; 85%.
C) 1%; 99%.
D) 90%; 10%.