Contribute correction: Kalkulation

 _    _      ___      ______   _    _   
| |  | ||   / _ \\   /_____// | || | || 
| |/\| ||  / //\ \\  `____ `  | || | || 
|  /\  || |  ___  || /___//   | \\_/ || 
|_// \_|| |_||  |_|| `__ `     \____//  
`-`   `-` `-`   `-`  /_//       `---`   
                     `-`