Let X,YX, YX,Y be continuous with joint PDF f(x,y)=12xyf(x,y) = 12xyf(x,y)=12xy for 0≤x,y≤10 \le x, y \le 10≤x,y≤1 with x+y≤1x + y \le 1x+y≤1. What is P(X+Y≤0.5)P(X + Y \le 0.5)P(X+Y≤0.5)?
132\frac{1}{32}321
116\frac{1}{16}161
164\frac{1}{64}641
18\frac{1}{8}81