Area of a Nut (Form Designer)

This is a form-based problem — open it in the Form Designer, not the code judge. An edit box (edtQ1_3) holds the width of a hexagonal nut, in cm, across its flats; a button (btnQ1_3) and a panel (pnlQ1_3) are already on the form. Write btnQ1_3's OnClick handler so that, given the flat-to-flat width d in edtQ1_3, it works out the nut's area (the hexagon minus the circular hole through its middle) and shows it on pnlQ1_3, rounded to one decimal place, formatted exactly like '45.3 cm squared'.

No input/output in the console sense. Grading sets edtQ1_3.Text to a width, clicks btnQ1_3 once, then checks pnlQ1_3.Caption. Formula: $\text{area}=\frac{3\sqrt{3}}{2}{d}^2-\pi {\left(\frac{d}{2}\right)}^2$, where $d$ is the value in edtQ1_3. Examples: d = 5 -> '45.3 cm squared' d = 10 -> '181.3 cm squared'