A rectangular frame has outside long-point dimensions 680×500 mm. Moulding face width is 40 mm. All corner mitres are 45°, so each inside dimension is outside dimension minus twice the face width. Cut all four pieces sequentially from one stock length, adding 4 mm allowance PER PIECE plus 20 mm at each stock end. Ignore defects and decorative pattern matching.
Calculate the inside opening perimeter in mm. Keep intermediate values unrounded; round the final answer to 4 decimal places if needed.
