!3 ''The type of the sales goods cannot be duplicated''

|''begin admin transaction''| Bill |
|''add sales item''|10|''of type''|cake|''costing''|3.00|''each''|
|'''reject'''|''add sales item''|10|''of type''|cake|''costing''|3.00|''each''|
|''complete transaction''|

|''sales item list''|
| ''name''| ''count'' |''selling price''|
|   cake  |    10     |    3.00         |
