The diagram presents an eyepiece graticule and a cell as seen with a microscope. At this magnification, when the eyepiece graticule was calibrated, the full length of the graticule shown spanned $12$ divisions on a stage micrometer scale. There were $100$ divisions in $10\,\text{mm}$ of the stage micrometer. What is the actual length of the cell?
- A$2.5\,\mu\text{m}$
- B$3.6\,\mu\text{m}$
- C$360\,\mu\text{m}$
- D$3\,\text{mm}$