Final answer:
Paul will spend a total of $12.65 on screws.
Step-by-step explanation:
To find out how much Paul will spend, we need to calculate the cost of each type of screw and then add them together. Let's assume the cost of size 6 screws is $2 per kilogram, the cost of size 1 screws is $1.5 per kilogram, and the cost of size 4 screws is $2.5 per kilogram.
For the size 6 screws, Paul will spend 2 kilograms * $2 per kilogram = $4.
For the size 1 screws, he will spend 1.6 kilograms * $1.5 per kilogram = $2.4.
And for the size 4 screws, he will spend 2.5 kilograms * $2.5 per kilogram = $6.25.
Therefore, Paul will spend a total of $4 + $2.4 + $6.25 = $12.65.