4 A small object is projected from a point \(O\) with speed \(V \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an angle of \(45 ^ { \circ }\) above the horizontal. At time \(t \mathrm {~s}\) after projection, the horizontal and vertically upwards displacements of the object from \(O\) are \(x \mathrm {~m}\) and \(y \mathrm {~m}\) respectively.

1. Express \(x\) and \(y\) in terms of \(t\), and hence find the equation of the path.
   The object passes through the point with coordinates \(( 24,18 )\).
2. Find \(V\).
3. The object passes through two points which are 22.5 m above the level of \(O\). Find the values of \(x\) for these points.