Create a Sphere with Radius=3 and place it near the head of the toothbrush.
In the Front Viewport create a Plane and - in the Top Viewport - move it so it aligns with the light blue part of the toothbrush. Convert it to an Editable Poly.
Enter the Edge Geometry Mode and Shift+Drag the left edge to create the shape of the light blue shape. Scale and move them until they fit the blueprint image. Then work with both Front and Top viewports to arrange the vertices in the Top Viewport as well. (Select the vertices in the Front Viewport but move them as needed in the Top Viewport).
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