Suppose you own a bicycle but haven't found the time to ride it much lately. These days, it is only worth $42 to you. One of your close friends, who recently got a job at the college bookstore two miles down the road, wants to take it off your hands. He offers you $70 for the bicycle, and you gladly accept. Your friend is also happy because he thinks the bicycle is worth $93.
How much total value was created from this trade?