Find the Condition on the Non-Negative Constants a and B $p ( x , y ) = \left\{ \begin{array} { c c } a x + b y & \text { if } 0 \leq x \leq 6,0 \leq y \leq 6 \\0 & \text { otherwise }\end{array} \right.$

Essay

Find the condition on the non-negative constants a and b for p(x, y)to be a joint density function, where $p ( x , y ) = \left\{ \begin{array} { c c } a x + b y & \text { if } 0 \leq x \leq 6,0 \leq y \leq 6 \\0 & \text { otherwise }\end{array} \right.$