Representation of data — practice question

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