A Plane Lamina with Constant Density $\rho ( x , y ) = 6$

A plane lamina with constant density $\rho ( x , y ) = 6$ occupies a region in the $x y$ -plane bounded by a simple closed path $C$ . Its moments of inertia about the axes are $I _ { x } = - \frac { \rho } { 3 } \int _ { C } y ^ { 3 } d x \text { and } I _ { y } = \frac { \rho } { 3 } \int _ { C } x ^ { 3 } d y$
Find the moments of inertia about the axes, if $C$ is a rectangle with vertices $( 0,0 ) , ( 4,0 )$ , $( 4,5 )$ and $( 0,5 )$ .

A) $( - 2,880,1,200 )$
B) $( 1000,640 )$
C) $( - 1,280,1,280 )$
D) $( 2,000 , - 1,280 )$
E) $( - 2,000,1,280 )$