$3$ Fig. $3\mathrm{.}1$ shows a boy throwing a ball at an object in a fairground.

Fig. $3\mathrm{.}1$

The ball has a mass of $190$ g and travels horizontally with a constant speed of $6\mathrm{.}9$m$//$s$.$ the momentum of the ball is about $1\mathrm{.}3$ km$/$s$.$ After hitting the object, the ball bounces back along the same straight path with a speed of $1\mathrm{.}5$ m $/$ s$.$ The object has a mass of $1\mathrm{.}8$ kg$.$ Calculate the speed of the object after it is hit by the ball. $($igcse physics level$)$