Question 733278


{{{A[1]=12m *16m=192m^2}}}

{{{A[2]=6m *3m=18m^2}}}

{{{drawing( 500, 500, -5, 20, -5, 20,
  grid(0),locate( 1, 1, A ),locate(16, 1, B),locate( 1, 12, C ),locate( 16, 12, D ),locate( 5, 4, E ),locate(12, 4,F),locate( 5,9, G ),locate( 12, 9, H ),line( 1, 1, 1, 12 ),line( 16, 1, 16, 12 ),line(1, 1, 16, 1 ),line( 1, 12, 16,12 ),blue(line(12, 4, 12, 9 )),blue(line( 5, 4, 12, 4 )),blue(line( 5, 4, 5, 9 )),blue(line( 5, 9, 12, 9 ),locate( 12, 6.5,shaded_area ),locate( 8, 3.5,shaded_area ),locate( 7, 10.5,shaded_area ),locate(1.2, 6.5,shaded_area ),locate( 16.5, 7.5,A[1]=192m^2 )),locate( 8, 7,A[2]=18m^2 )))
  
 }}}

shade the area between blue and black rectangle; that area is equal to {{{192m^2-18m^2=174m^2}}}