Costing sheets.

I would like someone who knows there maths, (work in fashion or interiors) idea interiors, I need someone who can work out the cost of making up cushions, I have had a go, but not sure it's correct and wasn't shown how to do it. The cushions as follows, one normal, i.e with a zip in cushions, the other is envelope cushion, (wrap) and one with a seam all round, I use silk, which cost's £10.00 per mtr, 54 ins wide, but would like it to be in cm's

I have also attached a file i.e costing sheet.

Just need or shown how to work out the cost!

cheers

jayc