
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
Residents in a certain city are charged for their water usage according to the following standards (water fees are paid monthly):

| Monthly Water Usage | Unit Price |
|---------------------|------------|
| Not exceeding 12m^3 | a yuan/m^3 |
| Exceeding 12m^3 but not exceeding 20m^3 | 1.5a yuan/m^3 |
| Exceeding 20m^3 | 2a yuan/m^3 |

(1) When a=2, a user consumes 15m^3 of water. Find the water fee the user should pay this month.  
(2) Let the water usage of a user be n cubic meters. Find the water fee the user should pay (expressed in terms of a and n).

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