使用自定义类对LINQ查询中的所有列求和

I'm new to using LINQ in VB.Net (within ASP.Net) and I can't seem to figure out how to Sum the data returned in the following query. In my actual code there are 26 items instead of just three and I use a custom class to organize them. I've found countless examples of how to sum a few individual items when selecting them individually but nothing on summing 26 separate columns organized in a class. I'm new to using LINQ in VB.Net (within ASP.Net