Average speed = Total distance ÷ Total time for both legs.<br><br>
&bull; Going: 2.4 km = 2400 m, time = 40 min<br>
&bull; Return: time = 2400 ÷ 75 = 32 min<br>
&bull; Total distance = 2400 + 2400 = 4800 m<br>
&bull; Total time = 40 + 32 = 72 min<br>
&bull; Average speed = 4800 ÷ 72 = 66.666... &asymp; 66.67 m/min<br><br>
Final Answer: 66.67 m/min