1. Navigate to Settings | Solutions | Packt.
2. Create a new field by clicking on Entity | Contact | Fields | New and enter the following details:
   • Display Name: Number of Activities
   • Data Type: Whole Number
   • Field Type: Rollup
3. Click on Edit next to the Field Type dropdown.
4. In the Rollup Field dialog, under Related Entity, select Activities (Regarding) and click the tick box.
5. In the Filters section, select the following:
   • Activity Status under Field
   • Equals under Operator
   • Value under Type
   • Check Open and Scheduled under Value
6. Click on the tick box.
7. Under Aggregation, select the following:
   • Aggregate Function under Count
   • Activity under Aggregated Related Entity field
8. Click on the tick box. Your ROLLUP FIELD dialog will look as follows:

9. Click on Save and Close on the ROLLUP FIELD dialog and the attribute dialogue.
10. Click on the Publish All Customizations button for your solution.