Two charges $2\mathrm{.}0\backslash$mu C and $+2\mathrm{.}0\backslash$mu C are separated by $4\mathrm{.}0$ cm on the z$-$axis symmetrically about origin, with the positive one uppermost. Two space points of interest P$1$ and P$2$ are located $3\mathrm{.}0$ cm and $30$ cm from origin at an angle $30\backslash$deg with respect to the z$-$axis. Evaluate electric potentials at P$1$ and P$2$ in two ways: $($a$)$ Using the exact formula for point charges, and $($b$)$ using the approximate dipole potential formula