Final answer:
To calculate the profit, multiply the number of packs by the cost of each pack to find the total cost. Multiply the number of pens sold by the selling price of each pen to find the total revenue. Subtract the total cost from the total revenue to find the profit.
Step-by-step explanation:
To calculate the profit Charles made, we need to first calculate the total cost of the pens and the total revenue from selling them.
The total cost is obtained by multiplying the number of packs by the cost of each pack, so 40 packs * £4.30 = £172.
The total revenue is obtained by multiplying the number of pens sold by the selling price of each pen, so £0.85 * 640 pens = £544.
To calculate the profit, we subtract the total cost from the total revenue, so £544 - £172 = £372.