4. A particle \(P\) projected from a point \(O\) on horizontal ground hits the ground after 2.4 seconds. The horizontal component of the initial velocity of \(P\) is \(\frac { 5 } { 3 } d \mathrm {~ms} ^ { - 1 }\).

1. Find, in terms of \(d\), the horizontal distance of \(P\) from \(O\) when it hits the ground.
2. Find the vertical component of the initial velocity of \(P\).
   \(P\) just clears a vertical wall which is situated at a horizontal distance \(d \mathrm {~m}\) from \(O\).
3. Find the height of the wall. The speed of \(P\) as it passes over the wall is \(16 \mathrm {~ms} ^ { - 1 }\).
4. Find the value of \(d\) correct to 3 significant figures.