(a) Since, seven equal cubes are joined and made a cuboid. So, length of cuboid = 7 x 5 = 35 cm breadth of cuboid = 5 cm and height of cuboid = 5 cm Now, surface area of resulting cuboid = 2 (lb + bh + hl) = 2 (35 x 5 + 5 x 5 + 5 x35) = 2(175 + 25 + 175) = 2 x 375 = 750 cm3