Five small multiples show monthly car sales per model in separate area charts, colored distinctly and outfitted with dots and hover tooltips. The code defines an `AreaChart` class using the D3 v7 API (`d3.scalePoint`, `d3.scaleLinear`, `d3.area`) to generate SVG paths and circles. Each chart's area path records total sales on mouseover, while each dot reveals the specific month and sales value, with hover effects changing fill and stroke color via CSS transitions.