A simplified grade point average (GPA) assigns grade points of 4 to an A grade, 3 to a B, 2 to a C, 1 to a D, and 0 to an F. A student named I M Smart is taking five 3-credit courses, has made A grades in four of them, and awaits the results of the fifth course. Smart is certain that the grade in the last course will be either an A or a B and sets the probability of an A at 0.8. Let X be Smart's final GPA and work out the values and probabilities of X in the two cases of an A and a B for the last course.