
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
A store purchases 1000 items at a price of 80 yuan per item (unsold items will become waste). Market research shows that when the price per item is 100 yuan, all items will be sold out; when the selling price increases by 1 yuan, the sales volume decreases by 5 items. To maximize profit, the store decides to increase the selling price by x yuan, resulting in a total profit of y yuan.
(1) Please express y as a function of x;
(2) At what selling price will the total profit be maximized, and what is the profit at this price?

Present the answer in LaTex format: \boxed{Your answer}
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