| Column Letters | Operation Used |
| Column A | Addition |
| Column B | Subtraction |
| Column C | Division |
| Column D | Addition |
| Column E | Multiplication |
| Column F | Subtraction |
| Column G | Multiplication |
| Column H | Division |
| Column I | Multiplication |
| Column J | Subtraction |
| Column K | Division |
| Column L | Addition |
| Column M | Multiplication |
| Column N | Division |
© Derek Cumberbatch