Nexample 5.4 and exercise 5.5, we considered the joint density of y1, the proportion of the capacity of the tank that is stocked at the beginning of the week, and y2, the proportion of the capacity sold during the week, given by f(y1,y2)= 3y1, 0≤y2≤y1≤1, 0, elsewhere. a find the marginal density function for y2. b for what values of y2 is the conditional density f ( y1 | y2 ) defined? c what is the probability that more than half a tank is sold given that three-fourths of a tank is stocked?