Each square in the grid below has area 1. Find the area of the irregular quadrilateral below. [asy] size( 200 ) ; int xmax = 9 ; int ymax = 8 ; path quad = (0,0)--(5,0)--(9,3)--(4,8)--cycle ; fill( quad , blue ) ; draw( quad , linewidth(2) ) ; for( int i=0 ; i<=xmax ; ++i ){ draw( (i,0)--(i,ymax) ) ; } for( int i=0 ; i<=ymax ; ++i ){ draw( (0,i)--(xmax,i) ) ; } [/asy]
