)The joint probability density function of X and Y is given by f(x, y)=\left\{\begin{aligned} \operatorname{exe}^{-(x+y)} &: x>0, \quad y>3 \\ 0 &: \text { otherwise } \end{aligned}\right. Are X and

Y independent? =) What if f(r, y) were given by f(x, y)=\left\{\begin{array}{ll} 2 & 0