
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 certain school's soccer team needs to purchase soccer balls of two brands, A and B. It is known that the unit price of brand A soccer balls is 20 yuan higher than the unit price of brand B soccer balls. Also, the quantity of brand A soccer balls that can be purchased with 900 yuan is equal to the quantity of brand B soccer balls that can be purchased with 720 yuan. 
1. Find the unit prices of brand A and brand B soccer balls.
2. If the soccer team plans to purchase a total of 90 soccer balls of brands A and B, with the quantity of brand A soccer balls not less than twice the quantity of brand B soccer balls, and the total cost of purchasing both brands does not exceed 8500 yuan. Let the number of brand A soccer balls purchased be denoted as m, and the total cost as W yuan. How many purchasing plans does the team have? Which purchasing plan will result in the lowest total cost, and what is the minimum total cost?

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