A boutique cinema in York can seat 85 customers for its main evening screening. The demand for tickets over three evenings is shown in the table below.
| Screening Evening | Quantity of tickets demanded |
|---|---|
| Friday | 62 |
| Saturday | 78 |
| Sunday | 54 |
Calculate the excess supply of seats if the quantity supplied during these three evenings totalled 255. You are advised to show your working.
