4. Two commercial vendors buy goods at the same price. After a week, the first vendor's price decreases by $10 \%$, and after another week, the price increases by $20 \%$, while the second vendor's price increases by $10 \%$ after two weeks. Which vendor's price is lower after two weeks?
4. Let the original price of the goods be $x$, then the price of the first vendor after two weeks is $x \cdot \frac{90}{100} \cdot \frac{120}{100}=1.08 x$. While the price of the second vendor is $x \cdot \frac{110}{100}=1.1 x$. Therefore, the price of the first vendor is lower. $(x>0)$.