# Exercise 1B
# Tax calculator.
# Each amount of money is expressed as a whole number of pounds.
#
# Author: David Watt.

allowance = 10000  # tax-free allowance

rate = 20          # tax rate (%)

def taxable (income):
    "Return True iff income exceeds the tax-free allowance."
    return (income > allowance)

def tax (income):
    "Return the amount of tax payable on income."
    if taxable(income):
        return (income - allowance) * rate // 100
    else:
        return 0