SQL query woes

So I have 3 tables:  "Project" and "Expenses" and "Report"   

What I need to do is insert into corresponding "report.id" row the sum of "expenses.AMT" based off "project.id" and "project.status" of active

For example, project 24 is an active status, and has expenses of 200 and 375, then it needs to enter 575 into the "report" table row that has "report.id" equal to 24.