how would I write a c++ if-else statement for the tax break?

A retail company must file a monthly sales tax report listing the sales for the month and the amount of sales tax collected. This program reads from an input file the month (string), the year (integer), and the total amount (real) collected at the cash register (product sales + sales tax). Sales tax consists of both a state sales tax and a city sales tax. For example, if the state sales tax is 4% and the city sales tax is 2%, the total sales tax would be 6%. Processing: If the total amount collected is known (and it is - was read from the input file) and the total sales tax is 6% (city & state), the amount of the product sales is calculated as: S = T / 1.06 where S is the product sales and T is the total income (product sales plus sales tax). To encourage growth of small businesses, a small business owner receives a tax break on state taxes. If product sales for the month are less than $100,000, the business is only responsible for 90% of the taxes it would pay if product sales had met or exceeded $100,000.