Received a cashier's check against the PNC Bank for $3940. I was to be a mystery shopper, spend $50 at McDonald's Fast Food, $90 at Wal-Mart, send a Western Union or Money Gram Transfer for $3100 and pay a service charge of $200, leaving me $500 for my effort. I called the PNC Bank and they said the check is not valid. Had I sent the $3100 without check this out, shame on me. I am reporting this to the USPS.