$\"\"$

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Let $\"\"$ be the number of $\"\"$ increases in price and $\"\"$ be the income.

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For each $\"\"$ increase in price, they will rent $\"\"$ fewer videos.

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The store rents $\"\"$ videos per week at $\"\"$ .

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If they increase the rent for every $\"\"$ increase, they will rent $\"\"$ fewer videos.

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So the income $\"\"$ is $\"\"$ .

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Hence the quadratic function is $\"\"$ .

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The standard form of quadratic function $\"\"$ , where $\"\"$ .

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$\"\"$ and $\"\"$ .

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Since $\"\"$ , the function has a maximum value and opens down.

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The equation of the axis symmetry is $\"\"$ .

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$\"\"$ (Substitute the values $\"\"$ and $\"\"$ )

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$\"\"$ (Simplify)

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The equation of the axis symmetry is $\"\"$ and $\"\"$ -coordinate of the vertex is $\"\"$ . $\"\"$

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Find the maximum price income the store at $\"\"$ .

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Multiply)

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$\"\"$ (Substitute: $\"\"$ )

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The maximum price is $\"\"$ income of the store.

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$\"\"$

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The maximum price is $\"\"$ income of the store.