Thickness of Wood =3cm Length =1.48m=148cm Breadth =1.16m=116cm Height =83cm Inner length = Outer length - twice width =148−6=142cm Breadth =116−6=110cm Height =80cm [ since it is open box] Area of inner surface =2(lb+bh+hl)−lb=2[142×110+110×80+80×142]−[142×110]=55940cm2=5.5940m2 The cost of painting its inner surface at ₹150 per m² So, The Cost of Painting its inner surface =150×5.5940m2=₹839.10