What is the allowance for double grooved seam / joint?

A. Width of folder edge + thickness of sheet

B. 2 times width of folder edges + 2 times thickness of sheet

C. 3 times width of folder edges + 3 times thickness of sheet

D. 4 times width of folder edges + 4 times thickness of sheet

Correct Answer: 4 times width of folder edges + 4 times thickness of sheet