Here's my solution:
Edit: Had to change / update my solution. Deceptively hard to make it so simple. And the challenge instructions should have said " no * Input tools allowed" :) Great way to get exposure to less frequently used tools. Thanks!
Tried to go for the "fewest number of tools" approach! And realized I'm spoiled by the variety of configuration options in the regular Join and Summarize tools... but this was the first time I have EVER used a Calgary tool, so super fun!