Let f(x,y)=2f(x, y) = 2f(x,y)=2 on 0≤y≤x≤10 \le y \le x \le 10≤y≤x≤1. Find P(X+Y≤1)P(X + Y \le 1)P(X+Y≤1).
1/21/21/2
1/41/41/4
2/32/32/3
1/31/31/3