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 %

Rationale: 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 = 80.2 % ans a
Answer: A