Third Grade Mysteries B: The Case of the Snack Shack

Third Grade Mysteries B: The Case of the Snack Shack

 Harborville's Beach Snack Shop had been open only an hour when Max stopped in and noticed a new poster announcing a price increase. "I put the sign up this morning," Mr. Levine told him. "Had to raise my prices ten percent because I have so many new expenses. Like now I need a new window for my back room. Somebody broke it, trying to get into my store last night."
"Have you called the police?" Max asked.
"No. Nothing was stolen." He led Max to a small storeroom in the back. "I use this space as an office. Sat here and made my price change poster last night. Soon's I was done, I left it on that old desk. When I went out, I locked the door to the main part of my store. So whoever got in was stuck in this little storeroom. Nothing here to steal."
When Max left he wandered down to the break wall, where Nathan and Trevor were fishing. "Did you hear that somebody broke a window at the Shack?" he asked.
"Nope," Nathan said. "We've been here since dawn. Haven't talked to anybody." Trevor gestured to the bucket. "We've caught some big ones." Nathan stood. "But now I'm starving. I've got a dollar left from my allowance. If Mr. Levine is there now, I'm going up to the Shack to get a Big Beach Bun."
"Better get another dime from somewhere," Trevor told him. "A dollar's not enough any more. As for me, I'm going home to get a couple sandwiches for myself."
"You both stay right here," Max said. "I know which one of you broke that window. You'd better think of a way to pay for it, because I'm telling Mr. Levine."

How did max figure it out?

Story: The Case of the Snack Shack by Carol Farley