Collision in electric field?

In a region , an electric field $E= 15N/C$ making an angle of $30°$ with the horizontal plane is present. A ball having charge $2C$ , mass $3 kg$ and coefficient of restitution with ground $\frac12$ is projected at an angle of $30°$ with horizontal in the direction of Electric field with speed $20 ms^{-1}$ . Find the horizontal distance travelled by the ball from first drop to the second drop. If your answer is of the form $a \sqrt{b}$ , where $a$ $\text{\&}$ $b$ are positive integers , then enter the value of $a+b$ .