for xy ≤ 1
|xy-1| = -xy+1
for xy> 1
|xy-1| = xy-1
xy ≤ 1
=> x≤ 1/y for 0≤y≤2
I =∫∫ |xy-1| dxdy
= ∫∫ -xy+1 dxdy ( 0≤x≤y ) + ∫∫ xy-1 dxdy (y