You drive on Interstate 10 from San Antonio to Houston, half the time at 79 km/h and the other half at 100 km/h. On the way back you travel half the...

You drive on Interstate 10 from San Antonio to Houston, half the time at 79 km/h and the other half at 100 km/h. On the way back you travel half the distance at 79 km/h and the other half at 100 km/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?