Function for simple calculation of tax surcharges and discounts. A previously saved tax rate can be added to or subtracted from an amount by pressing a button. The profit calculation enables the determination of costs, sales price and margin. The transparent display facilitates mainly commercial calculations. Change of sign, for example from 100 to 100 or vice versa, by pressing a button. Valuable function for each calculation that starts with a negative number. Surface with particularly durable properties. Even at high loads, the heavy-duty metal front can be relied on. The devices are solar-powered and are supported, if needed, by battery operation. If the computer is not used for 6 minutes, it switches off automatically.This text is machine translated.