A1. In the factory, the equipment was upgraded and productivity increased by $25 \%$. When some workers were laid off, productivity decreased by $20 \%$. By what percentage did productivity change in this factory after both changes?
(A) Decreased by $5 \%$
(B) Decreased by 2.5\%
(C) Decreased by 2 \%
(D) Did not change
(E) Increased by $5 \%$
A1. If at the beginning the factory produced $x$ products, then after the equipment was updated, they produced $\frac{125}{100} \cdot x$ products, and after the layoffs, they produced $\frac{80}{100} \cdot \frac{125}{100} \cdot x=x$ products. The number of final products has therefore not changed. The correct answer is $D$.