What will be the field intensity of Electrical dipole on axial line?

Lets take an example of two point charges i.e. –q and +q. Both are separated by a distance of 2a. So, if we want to calculate the Electric field intensity electrostatic 1.39 at some point say P present on the axial line of the electric dipole. Then the distance from the center of the dipole will be OP=r. See the figure below.