Surface area: (12 * 5+12 * 8+5 * 8) * 2 = 9296cm2.

(2) Length: 24 cm, width: 5 cm and height: 4 cm.

Surface area: (24*5+24*4+5*4)*2=4648 cm2.

(3) Length12cm, width10cm and height 4cm.

Surface area: (12 *10+12 * 4+10 * 4) * 2 = 4304cm2.

Hope to adopt!