As shown in the picture: a rectangular sheet of iron, 30cm long and 20cm wide, subtracting a small square with 4cm side length from four corners, and then folding it along the dotted line to make a box without a cover. How many milliliters is the volume of the box? How much sheet iron is actually used to make the box? (I have no picture, understanding)

As shown in the picture: a rectangular sheet of iron, 30cm long and 20cm wide, subtracting a small square with 4cm side length from four corners, and then folding it along the dotted line to make a box without a cover. How many milliliters is the volume of the box? How much sheet iron is actually used to make the box? (I have no picture, understanding)

Height of cuboid: 4cm
Length of cuboid: 30-4 * 2 = 22 cm
Cuboid width: 20-4 * 2 = 12cm
Cuboid volume: 22 * 12 * 4 = 1056 cm3
Actual iron sheet area = 30 * 20-4 * 4 * 4 = 536 square centimeters