Suppose that a certain country conducted tests of a certain type of bomb in 2009 and 2013, and another country's defence ministry estimated their power at between 6 and 8 kilotonnes of a certain explosive in 2009 and between 8 and 9 kilotonnes of the explosive in 2013. "The power of the country's bomb tests increased between 2009 and 2013," stated a commentator. Assume that the ranges given by the second country's defence ministry represent the ranges within which the actual power of the tests lies with a probability of 0.8. Also assume that the defence ministry's estimates are Normally distributed. Complete parts (a) and (b) below.
a. What is the probability that the actual power of the 2009 test was greater than 9 kilotonnes of explosive?
b) What is the probability that the actual power of the test was higher in 2009 than in 2013?