def calc_monthly_expense(income):
    """
    Calculate the user's monthly expense based on income.

    All budgets are expressed in decimals.
    """
    housing_budget = 0.28
    misc_budget = 0.36
    cushion_budget = 0.10
    monthly_expenses = (income * (housing_budget + misc_budget +
                        cushion_budget)) / 12
    return monthly_expenses