Representation of data — practice question

The bow is formed from a uniform curved section $AB$ of mass $1.4\,\text{kg}$, together with a uniform taut string of mass $m\,\text{kg}$ joining $A$ to $B$. The curved section $AB$ is an arc of a circle with centre $O$ and radius $0.8\,\text{m}$. The angle $AOB$ is $\frac{2\pi}{3}$ radians (see diagram). The centre of mass of the bow, including the string, is $0.65\,\text{m}$ from $O$.