Factory X's bulbs work for over 5000 hours in 79% of cases, whereas factory Y's bulbs work for over 5000 hours in 85% of cases. It is known that factory X supplies 80% of the total bulbs available. What is the chance that a purchased bulb will work for longer than 5000 hours? Choose the correct choice from the following answers
A) 80.2%  B) 88%  C) 87.4%  D) 85%  E) 83.9%
For X, 80% of 79% will work.   For Y, 20% of 85% will work. *20% is the rest of the bulb supply in the market.   So, the probability that a purchased bulb will work is:   0.80(0.79) = .632   0.20(0.85) = 0.17   The combined probability then is 63.2 + 17= 
<gadget id="calculator">63.2 + 17</gadget>
<output>80.2</output>
80.2%   80.2%NS 80.2%
<result>A</result>
Factory X's bulbs work for over 5000 hours in 79% of cases, whereas factory Y's bulbs work for over 5000 hours in 85% of cases. It is known that factory X supplies 80% of the total bulbs available. What is the chance that a purchased bulb will work for longer than 5000 hours?