text: ## Intermediate Algebra (6th Edition)
  
  From part (a) we have: $\begin{array}{ccccc} \\x &10 &100 &1000 \\\\\dfrac{100x+5000}{x} &600 &150 &105 \end{array}$ Based on the values in the table above, the cost per bookshelf, which is represented by $\dfrac{100x+5000}{x}$, decreases as the number of bookshelves manufactured (represented by $x$) increases. Based on the given expression, the value of $\dfrac{100x+5000}{x}$ decreases as $x$ increases because the denominator increases proportionally faster than the numerator. Industry-wise (situation-wise), the cost per bookshelf decreases because the cost of production gets smaller as more bookshelves are manufactured.