The following shall be the measure of damages to be followed by the jury or judge who determines the issue of just compensation:
If only a part of a tract is taken, the measure of just compensation for the taking shall be the difference between the fair market value of the entire tract immediately before the taking and the fair market value of the remainder immediately after the taking, with consideration being given to any special or general benefits resulting from the utilization of the part taken for transportation purposes.
If the entire tract is taken the measure of just compensation for the taking shall be the fair market value of the property at the time of taking.