In the given figure, $ABCD$ is a quadrilateral inscribed in a circle with centre $O$. $CD$ is produced to $E$ such that $\angle ADE=95°$ and $\angle OBA=30°$. Find $\angle OAC$.

Mark the correct alternative in each of the following:

If the length of a chord of a circle is $16 \mathrm{cm}$ and is at a distance of $15 \mathrm{cm}$ from the centre of the circle, then the radius of the circle is

If $O$ is the centre of a circle of radius $r$ and $AB$ is a chord of the circle at a distance $\frac{r}{2}$ from $O$, then $\angle BAO=$

$ABCD$ is a cyclic quadrilateral such that $\angle ADB=30°$ and $\angle DCA=80°$, then $\angle DAB=$