Finding the strength of electric field between two charges

Electric Field problem? Please help?

Point P lies in between charges A and B. A has a charge of 30, and B has a charge of 10. P is .2m away from A, and .5m away from B. Determine the electric field strength at point P

Answer:

Let us say the position is like this:

A P B


electric field caused by A:

E=k*q/(r^2)=9*10^9 * 30 / (2^2)= 6.75*10^10 N/C (direction is to the right)

electric field caused by B:
E=k*q/(r^2)=9*10^9 * 10 / (5^2) =3.6*10^9 N/C (direction is to the left)

So, the total electric field at P is:
6.75*10^10 - 3.6*10^9= 6.39*10^10 N/C (the direction is to the right)