Please reason step by step, and put your final answer within \boxed{}.
Bill has a take-home salary of $55,000. He pays $2,500 in property taxes, $3,500 in sales taxes, and contributes 6% of his gross salary to his retirement fund. Additionally, Bill is subject to a progressive income tax system with the following rates: 

- 10% on the first $20,000 of his gross salary
- 15% on the amount from $20,001 to $40,000
- 25% on the amount from $40,001 and above

Considering these taxes, deductions and contributions, what is Bill's gross salary?
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