Target costing question

Brief: I am confronted with the following question but a part of the answer does not make sense to me can you please help me understand this:

My area of confusion is given in the curly braces {} in the answer section.

Question: Given the following information what is the target cost gap for Product X?

Target Selling Price per unit $10
Target Profit 25% on cost
Current Cost $8.40 per unit

Answer Given:

Target Profit (25% of cost = 20% of sales price) = $2
{My question is how is 25% of cost equal to 20% sale price}

Target cost $10 – $2 = $8
Target cost gap = $8.40 – $8 = $0.40