In the cost card, the total cost of parts is $40 per unit. Obviously a webcam will be using lots of parts.
80% of these parts can be be replaced by standard parts which cost 55% less. Therefore at the moment they cost 80% x $40 = $32 per unit, but in future will only cost 32 – (55% x 32) = $14,40.
The other 20% of the parts cost at the moment 20% x $40 = $8 per unit, However they can be bought from an alternative supplier and will then only cost 8 – (10% x 8) = $7.20
Therefore the total cost of parts is 14.40 + 7.20 = $21.60 per unit.