3 2-dimensional normal distribution (5p) Suppose X is the height and Y is the weight of a dwarf student in a university. Furthermore suppose : 155, rx = 2.5, that X and Y follow a bivariate normal distribution with parameters x = 69, = oy = 20 and correlation p = 0.55. Let us assume that the fitness score of a student dwarf is computed as his weight minus his height. What is the probability that the total fitness score of 4 students will be no smaller than 360 and no bigger than 400?