A5-1b bag of apples costs $4.00
so, the unit price is $ 4/5 per apple
And an 8-1b bag of the same type of apples costs $6.00
so, the unit price is $6/8 per apple
So,
The constant proportionality for the first bag
the constant proportionality for the second bag
The difference = 0.8 - 0.75 = 0.05