Answer:
Step-by-step explanation:
[tex]N_{x}=970-\frac{3780}{x}\\\\=N^{i}_{x}=0-3780\frac{d}{dx}\frac{1}{x}\\\\=-3780(\frac{-1}{x^{2}})\\\\=\frac{3780}{x^{2}}\\\\N^{i}_{10}=\frac{3780}{100}\\\\=37.8\\\\N^{i}_{20}=\frac{3780}{400}\\\\=9.45[/tex]
There is an inverse relationship between the amount on advertisement and average number of bower boats