a statistics course is taught by two different departments d1 and d2. historical records show that the course grades for students taking it from d1 follow a population with distribution n(150, 50), and those taking it from d2 follow a n(140, 40) distribution, assumed to be independent 4 of the records from d1. this year 25 students take the course from d1 while 16 students take it from d2. what is the probability (find the closest answer) that those taking it from d1 have a higher average course grade?