
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
The monthly fee for mobile phones usually consists of a monthly rental fee and a call charge. As China Mobile's core brand, "Global Call" has the highest number of users among all brand cards nationwide. Its charging standard is: a monthly rental fee of 50 yuan and a call charge of 0.4 yuan per minute. The introduction of "Shenzhouxing" broke the traditional mobile phone payment model, being the first to achieve zero monthly rental (monthly rental fee of 0 yuan), but the call charge of "Shenzhouxing" is higher than that of "Global Call", with a call charge of 0.6 yuan per minute. Considering only the monthly rental fee and call charge, answer the following questions:
(1) Please write out the monthly consumption $y$ (in yuan) as a function of the call duration $x$ (in minutes) for both "Global Call" and "Shenzhouxing". (It is not necessary to specify the range of the independent variable.)
(2) If you are a mobile phone user, from the perspective of economic benefits, how should you decide whether to use "Global Call" or "Shenzhouxing" based on your monthly call duration? Please explain by categorizing.

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