The publisher

The publisher prepares the release of the dictionary. No matter the number of printed copies, preparation costs are 150000 CZK. The printer charges 80 CZK for one print.
A) What are the costs of one dictionary if 5000 copies are printed?

B) For what number of dictionaries will the costs for one issue of CZK 95 be?

Correct answer:

a =  110 Kc
b =  10000

Step-by-step explanation:

$$\begin{gathered} f(n)=(150000+80n)/n=150000/n+80 \\ a=f(5000) \\ a=150000/5000+80=110\text{Kc} \end{gathered}$$

$$\begin{gathered} f(b)=95 \\ 150000/b+80=95 \\ 150000+80\cdot b=95\cdot b \\ 15b=150000 \\ b=\frac{150000}{15}=10000 \\ b=10000 \end{gathered}$$

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