The perpendicular bisector of the line segment joining the point $A(1, 5)$ and $B(4, 6)$ cuts the $y$-axis at

The coordinates of the point which is equidistant from the three vertices of the $∆AOB$ as shown in the figure are

$AOBC$ is rectangle whose three vertices are $A(0, 3), O(0, 0)$ and $B(5, 0)$. The length of its diagonal is

The perimeter of a triangle with vertices $(0, 4), (0, 0)$ and $(3, 0)$ is

The area of a triangle with vertices $A(3, 0), B(7, 0)$ and $C(8, 4)$ is