How do I solve this equation my professor gave me?

[moeug1999]

Homework Statement

A 1.82 10-9 C charge has coordinates x = 0, y = −2.00; a 2.88 10-9 C charge has coordinates x = 3.00, y = 0; and a -4.90 10-9 C charge has coordinates x = 3.00, y = 4.00, where all distances are in cm. Determine magnitude and direction for the electric field at the origin and the instantaneous acceleration of a proton placed at the origin.
(a) Determine the magnitude and direction for the electric field at the origin (measure the angle counterclockwise from the positive x-axis).

(b) Determine the magnitude and direction for the instantaneous acceleration of a proton placed at the origin (measure the angle counterclockwise from the positive x-axis).

Relevant Equations

Coulombs Law (?)

My professor does not walk us through the problem. He literally just gave us an equation and that's it. I do not know how to do this problem.

 

[kuruman]

According to our guidelines, you must show some effort towards solving the problem. We do not provide solutions. If you want to be "walked through", you need to get up first and start walking. This means that you should post the equation that your professor gave you and include your own thoughts and strategies about how to apply it to answer the questions posed by the problem. If you are headed in the wrong direction, we will point it out.