The cost for labor is 10$ per hour.
25$ of raw material + 10$ of supplies + 5$ of shipping + one hour of assembly at 10$/hour = $ 50.
Your cost of sales is 50.00 $ per unit.
Warning: if the labor used to assemble "Product A" is paid even if there is no production, then he is an employee and must be budgeted in the menu "Employees". Consequently, his cost should not be considered in your cost of sales as it is already budgeted in the menu "Employee". Your cost of sales would then be $ 40.00 per unit.