Each of 12 refrigerators of a certain type have been returned to the distributor because of loud noise. Suppose that 7 of these have defected compressor and 5 have a broken ice cube tray. The refigerators will be excamined one by one in ramdon order. Let X be number amoung the first 6 examined that have a defective compressor. Calculate :
1) P(x=5)
2) P(<= 4)
3) The expected value ot X