what is the estimated cost of repairing a loose exhaust heat shield in my 2007 Pontiac Vibe?

What is your question?

When I drive the car the loose heat shield bangs up against the exhaust pipe producing a hollow drum sound. I went under my car and saw that the bolt that originally held the shield tightly to my car's underside broke off from the bracket on the gas tank strap.

What makes this problem better or worse?

hitting a bump in the road

How long has your 2007 Pontiac Vibe had this problem?

for a few days