Exercise 7, § 2

Give an example of two convex sets $A \subset \mathbf{R}, B \subset \mathbf{R}^2$, such that the image of the convex set $A \times B$ under the bilinear mapping $(\lambda, x) \mapsto \lambda x$ of $\mathbf{R} \times \mathbf{R}^2$ in $\mathbf{R}^2$ is not convex.