{"type":"rich","version":"1.0","title":"1 / a + 1 / b = 1 / R + 1 / k","html":"<iframe src=\"https://www.desmos.com/calculator/ueu0vgv7jk?embed\" width=\"500px\" height=\"500px\" style=\"border: 1px solid #ccc\" frameborder=0></iframe>","width":500,"height":500}