All of these features and the value for money (there was a special offer at the supermarket around the corner), I have decided for the calculator. After a few years in use I dispose of him now. The disadvantage is that it is operated with button cells and not with solar cells. The operating time with the Knopfzelllen is excessively long. To replace the batteries the housing must be screwed. It shows the less good quality of the device. After replacing the button cell, the LCD display, however, had a loss of one line, so that could be worked on. When the calculator a few months was not in use, one of the coin-cell has leaked and has dissolved a metal contact strips. However, a repair is possible, me too delicate. Therefore, the calculator will be replaced with a solar-powered device brand.