Each of 13 refrigerators of a certain type has been returned to a distributor because of an audible, high-pitched, oscillating noise when the refrigerators are running. suppose that 8 of these refrigerators have a defective compressor and the other 5 have less serious problems. if the refrigerators are examined in random order, let x be the number among the first 6 examined that have a defective compressor. (a) calculate p(x = 4) and p(x ≤ 4). (round your answers to four decimal places.)