Problem Solving

I own a cafe'. The 1st day I opened no one come in. The 2nd day 5 people came in; the 3rd day 10 people came in and the 4th day 15 people. Also people left their business card for a free lunch. On the 1st day 0; the second day 3 people left their card; and each following day, 3 more people left business cards than the previous day. If this pattern continues what is the difference between the total number of customers and the total number of business cards after a full year (365 days)?