The average rate of change when \( x = 103 \) is \( \$0.00 \) per unit, the average rate of change when \( x = 101 \) is \( \$0.00 \) per unit, and the instantaneous rate of change is \( \$0.00 \) per unit.
Thus, the final answers are:
\[
\boxed{0.00 \text{ (for both average rates)}}
\]
\[
\boxed{0.00 \text{ (for instantaneous rate)}}
\]