Maaser

Question

In calculating my income for maaser I was wondering if the following items should be taken into account: Income Items: 1) Salary 2) Contributions to 401(k) made by employer 3) Cash Gifts 4) Non-cash gifts Expenses: 1) Mortgage/Rent 2) Tuition 3) Income Taxes 4) Gas/Electric 5) Telephone bill/Cell Phone Bill 6) Property Taxes 7) Health Insurance 8) Life Insurance 9) Homeowner's/Renter's 10) Clothing 11) Groceries 12) Car Payments/Insurance I know this is a long question, thank you in advance for answering. If the answer depends in any part on a "reasonable" or "average" amount, how does one determine this. Thank you again for the website.