A offered 3 units of a certain product for sale at a certain price. $B$ offered 3 units of the same product at the following price: 20% of the amount for which two units, plus 30% of the amount for which three units, plus 40% of the amount for which four units were sold at $A$. For this, $A$ offered a 10% discount on the price. Which trader is cheaper? Which one is cheaper if, after $A$'s discount, $B$ maintains his offer based on the new, reduced prices?
If $A$ offers $1 \mathrm{q}$ of goods for $x$ Ft, then according to the problem, $B$ offers $1 \mathrm{q}$ of goods for

$$
\frac{\frac{2 x \cdot 20}{100}+\frac{3 x \cdot 30}{100}+\frac{4 x \cdot 40}{100}}{3}=\frac{29}{30} x(\sim 0.97 x)
$$

Ft, which is $\frac{1}{30}$ of $x$ Ft less than $x$ Ft. Therefore, $B$ is the cheaper option.

A 10% discount on $x$ Ft means giving up $\frac{1}{10}$ of $x$ Ft, so in this case, the offer from trader $A$ is the cheaper one.

If $B$ maintains its offer even after the new, delivered price, applying the result obtained at the beginning of the solution, $B$ will ask for $\frac{1}{30}$ of the delivered price less, and thus, $B$ will again be the cheaper option.