Answer
The fee paid for 20 days during the holiday rush is $\$3050$.
Work Step by Step
For the rental business, it can be represented by an arithmetic sequence, with $a_{1} = 200$ and $d = -5$, which the general term $a_{n} = 200 + (n - 1)(-5)$, where n is the number of days taken for the rental.
The fee paid for 20 days during the holiday rush is
$\sum\limits_{n=1}^{20} a_{n} = \sum\limits_{n=1}^{20} [200 + (n - 1)(-5)]$
= $\frac{20}{2}(200 + a_{20})$
= $\frac{20}{2}(200 + 105)$ ($\because a_{20} = 200 + (20 - 1)(-5) = 105$)
= $\$3050$
