Let XXX and YYY be continuous random variables with joint PDF f(x,y)=6xf(x,y) = 6xf(x,y)=6x for 0≤y≤x≤10 \le y \le x \le 10≤y≤x≤1. What is E[Y]E[Y]E[Y]?
14\frac{1}{4}41
13\frac{1}{3}31
25\frac{2}{5}52
15\frac{1}{5}51