You drive on Interstate 10 from San Antonio to Houston, half the time at 50 km/h and the other half at 88 km/h. On the way back you travel half the distance at 50 km/h and the other half at 88 km/h. (a) What is your average speed from San Antonio to Houston? (c) What is your average speed for the entire trip? (d) What is your average velocity for the entire trip?