Arrest, Search Warrants, and Probable Cause

Mr. A walks into a police station, drops three wristwatches on a table, and tells an officer that Mr. B robbed a local jewelry store two weeks ago. Mr. A will not say anything else in response to police questioning. A quick investigation reveals that the three watches were among a number of items stolen in the jewelry store robbery. Do the police have probable cause to do any or all of the following?
1. Arrest Mr. A
2. Arrest Mr. B
3. Search Mr. A's home
4. Search Mr. B's home