From his home, Gene walked for 40 minutes to reach the library.<br>The library was 2.4 $$km$$ from his home.<br>On his return journey, he ran at a speed of 75 $$m/min$$. <hr> What was his average speed when he was walking to the library? <br> <input min="0" type="number" id ="imp6pg164q8a_1" class="lineinput" placeholder="?" /> $$m/min$$