A sphere of $2\,kg$ is released from a height of $5\,m$ with respect to the ground. After the collision which lasted $0.1\,s$ the sphere bounces with a speed of $5\,\frac{m}{s}$. Find the modulus of the average force in $N$ which the sphere gets from the floor. You may consider that air resistance is negligible and use $g=10\,\frac{m}{s^2}$.

The alternatives given in my book are as follows:

$\begin{array}{ll}

1.&300\,N\\

2.&400\,N\\

3.&320\,N\\

4.&420\,N\\

5.&280\,N\\

\end{array}$

Here I'm totally lost at. The only thing relevant which I can recall is that:

$\vec{J}=\overline{\vec{F}}\Delta t$

But I don't really know how to put the information given into this equation or if it will be relevant in the solution of the problem. Can somebody help me here?.