Saflok is an electronic door lock system made in Troy, Michigan, and used in modern hotels and other establishments. To open a door, you must insert the electronic card into the lock slip. Then a green light indicates that you can turn the handle and enter; a yellow light indicates that the door is locked from inside, and you cannot enter.
Suppose that 90% of the time when the card is inserted, the door should open because it is not locked from inside. When the door should open, a green light will appear with probability 0.98.
When the door should not open, a green light may still appear (an electronic error) 5% of the time. Suppose that you just inserted the card and the light is green. What is the probability that the door will actually open?