I need to create a spreadsheet to calculate a sales bonus for one person. The parameters are as follows:

If sales >0<20000 then Bonus = 5% of total sales

If sales >20000<=400000 then Bonus = 5% of first 20000 and 10% of sales >20000

If sales >40000<=60000 then Bonus = 5% of first 20000, 10% of next 20000 and 15% of sales >40000

If sales >60000 then Bonus = 5% of first 20000, 10% of next 20000, 15% of next 20000 and 25% of sales >60000

Thanks for any advice.