Answer:
(A)

Explanation:
- Width = 10cm
- Height = 6cm
- Depth = 15 cm
Volume of the solid box

Since the box tube is constructed out of 1 cm thick metal, we subtract 1cm on both sides of the width and height.
See the attached diagram for illustration.
- Internal width of the box = 10-2=8cm
- Internal height of the box = 6-2=4cm
However, the depth of the box remains unchanged, therefore:
- Internal depth of the box =15cm
Internal Volume of the box

Volume of metal used = Volume of Solid Box - Internal Volume
=900-480
=

The correct option is A.