Progressive Tax

The variable income is a yearly income in dollars. Tax is progressive: the first 10000 is tax free, the part from 10000 up to 40000 is taxed at 10 percent, and everything above 40000 is taxed at 20 percent. Use an if / else if / else chain to compute the tax into a variable called tax, remembering that a high earner still pays the lower rate on the lower band, then print Tax: <tax>.