Gotham City subway trains are always late for weekday morning commuters. In fact, the morning late times are approximately normally distributed, and the subway trains are, on average, 8 minutes late with a standard deviation of approximately 2 minutes. Suppose two morning subway trains are randomly and independently selected. (Approximate each answer to four digits after the decimal place)
a. What is the probability that the sum of their minutes is late is less than 10 minutes?
b. What is the probability that the second subway train is at least 2 minutes later than the first subway train selected?