How to calculate final sale price

I need a formula to calculate the price I need to charge for my product in order to net a specific amount.

I want to be able to enter the amount I want to net where I know the percent that my charge card company is charging to process the transaction.

Example: I want to net $90.00 on the sale. What should I set the sale price at if the processing company is charging 3.5% plus .15 cents per transaction?

Any help would be greatly appreciated.

Anthony