7. Say you have three (3) independent circuit boards. The life span of each circuit board follows a continuous uniform distribution on the interval (0,100) hours. Thus a=0 hours and b=100 hours. Let X1, X2 and X3 signify each boards life span respectively. a. What is the probability that exactly one of the circuit boards lasts more than 75 hours? Meaning the other two last less than 75 hours. b. What is the probability that all of the circuit boards will last more than 75 hours