Want to create date scripted field which will show addition of Time to First Response and Time to Resolution based on Calendar of a respective SLA

Hi Developer Community,
I want to create scripted date calculated field which will show the addition of Time to first Response and Time to Resolution .e.g.I want to create Estimated Date field(date type) and my time to first response is 8 hrs and Time to resolution is 8 hrs so my Estimated Date should show the value i.e. date for tomorrow or day after tomorrow like 27/08/2020.Can someone help me to how to do this.Your help is more appreciable.