4. \(\quad \mathbf { i }\) and \(\mathbf { j }\) are perpendicular unit vectors in a horizontal plane. A body of mass 1 kg moves under the action of a constant force \(( 4 \mathbf { i } + 5 \mathbf { j } ) \mathrm { N }\). The body moves from the point \(P\) with position vector \(( - 3 \mathbf { i } - 15 \mathbf { j } ) \mathbf { m }\) to the point \(Q\) with position vector \(9 \mathbf { i } \mathrm {~m}\).

1. Find the work done by the force in moving the body from \(P\) to \(Q\).
2. Given that the body started from rest at \(P\), find its speed when it is at \(Q\).