You drive on interstate 10 from san antonio to houston, half the time ai 55km/h and the other half ai 90km/h. what is your average speed (a) from san antonio to houston, (b) from houston back to san antonio, and (c) for the entire trip? (d) what is your average velocity for the entire trip? (e) sketch x versus t for (a), assuming the motion is all in the positive x direction. indicate how the average velocity can be found on the sketch.