Cai left his house at time zero and drove to the store, which is 4 blocks away, at a speed of 1 block per minute. Then he stopped and went into the store for 6 minutes. From there, he drove in the same direction at a speed of 1 block every 3 minutes until he got to the bank, which is 2 blocks away from the store. He stopped at the bank for 3 minutes. Then he drove home at a speed of 1 block every minute. Make a graph of showing the number of blocks away from home that Cai is a minutes after he leaves his house, until he gets back home.