How is it that no one responded to this question? For the benefit of other users, here's a response, just over 8 months late, hehe

begin by graphing the region (see below)

the line connecting (0,1) and (1,0) is

the line connecting (1,0) and (3,3) is

the line connecting (0,1) and (3,3) is

clearly we have to split this region into two parts: i will split it up into two intervals, [0,1] and [1,3].

Thus,

And continue ... what? ou expected me to give the whole solution away?