Congratulations to Jed of the 4th grade, and Micaela, Cole, Roberto, Maddie, and Jonah W. of the 7th grade for breaking the problem up into 4 cases and proceeding with the following plan: Jonah W. writes, "if anyone sees three whites, he will guess black within the first 5 seconds. If no lights go on in the first 5 seconds (there are at least 2 blacks), guess black if you see 1 black and 2 whites. If no lights go on within the first 10 seconds (there are at least 3 blacks), guess black if you see two blacks and one white. If no light goes on in the first 15 seconds (there are exactly 4 blacks), guess black." In any of the first three scenarios hold, guess white after the first wave of guesses passes and the time interval ends.