Representation of data — practice question

A cylinder with height $0.9\text{ m}$ and radius $0.9\text{ m}$ is set centrally on the top face of a cylinder with height $h\text{ m}$ and radius $r\text{ m}$, where $r < 0.9$, with the plane faces in contact and their axes lying on the same vertical line $AB$, where $A$ and $B$ are the centres of the plane faces of the cylinders. Both cylinders are uniform and are made of the same material. The lower cylinder is slowly tilted, and when the axis of symmetry is inclined at $45^\circ$ to the horizontal the upper cylinder is just on the point of toppling without slipping.