Here is some more evidence that Matthew was written before Mark. For convenience I used two paperclips to save my place in Matthew's, Mark's and Luke's versions of the passion week.
After Jesus clears the temple, all three Synoptics record that the Jewish leaders wanted to know where his authority came from. Jesus asks in response whether John's ministry was from God or not, and the leaders can't answer him because they'd rejected John, even though the people had accepted him.
In Matthew, Jesus goes on to illustrate, with a parable, their exclusion from the Kingdom because of their rejection of John (The parable of the Two Sons). Matthew then records two more parables, the Tenants and the Wedding Banquet.
Mark and Luke, however, only record the parable of the Tenants at this point.
Mark states, "Jesus began to speak to them in parables (plural)".
Yet he only gives one parable. Somehow he knows that Jesus told more than one at that point, and has omitted some.
Consider two scenarios: it is possible that Matthew, if he was using Mark, decided to add in the two parables which Mark had omitted. In this case, Mark, writing first, somehow knew there was more than parable, but chose only to record one. And Matthew knew exactly which extra parables Jesus told at that point, and added them in: the parable of the two Sons follows naturally after the question about Jesus' authority.
The alternative is that Matthew wrote down all three parables, and Mark, using Matthew as his source, stated that Jesus spoke in parables (plural), then recorded one of them.
In my view, the latter scenario fits best because it answers the question of how Mark knew about other parables (he had Matthew's gospel in front of him).
Mark would naturally choose the parable of the Tenants out of the three, because it mentions the Son, and this would illustrate to Mark's non- Jewish readers, the rejection of God's son by the Jewish leaders.