Step-by-step explanation:
(d) The probability that each specimen has hardness less than 73.84 is p = Φ((73.84 − 70)/3) = Φ(1.28) = . 9. So out of 10 independent specimens, the probability that 8 or fewer have hardness less than 73.84 is B(8,10,. 9) = 0.2639.
