
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
Crude oil needs to be cooled and heated to refine it into various products such as gasoline, diesel, plastic, etc. If the temperature of the crude oil (in degrees Celsius) at the $x^{th}$ hour is given by the function $y = f(x) = x^2 - 7x + 15$ ($0 \leq x \leq 8$), then the instantaneous rate of change of the temperature at the $4^{th}$ hour is $\_\_\_\_\_\_$ $^\circ C/h$; and the temperature of the crude oil in the vicinity of the $4^{th}$ hour is $\_\_\_\_\_\_$.

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