In assessing compensatory damages for legal remedies in tort, what is unavoidability?

Hypo 1: Bob has an old banged up car. Sam runs an auto repair shop. One day, Bob brings his car in to get it serviced. Sam negligently damages Bob's brakes. After Bob picks his car up, he notices the brakes aren't working correctly while leaving Sam's parking lot. Bob has a hot date that night, however, and can't be without his sweet ride. He figures he can have Sam deal with it later. That night, on his way to pick up Jill for their date, Bob's brakes fail and he slams into a tree, destroying his car. Result: Sam is liable for the damages he caused to Bob's breaks, but Bob shares some responsibility for his car being destroyed since he noticed his brakes were defective immediately after picking the car up and willingly chose to continue driving the car. Many of his damages were avoidable and it would be unfair to say Sam is solely responsible for Bob's stupidity.

Hypo 2: Amy hires Jill to replace the locks on her front door but, after removing the old locks, Jill decides that she was never really cut out for this type of work. She tells Amy she can't finish it, leaves halfway without installing the new locks, and gets on a bus to New York to audition for a Broadway show. 2 weeks later, because the doors don't have locks, someone breaks in and robs Amy. Amy sues Jill for damages. Result: Amy might have a case against Jill for the cost of hiring a new locksmith, but Jill's not responsible for the stolen goods. Amy has a duty to mitigate the damage of Jill failing to replace the locks by finding another locksmith or blocking her front door in the meantime. Here, she apparently did nothing about the fact that Jill didn't complete the job for 2 weeks, which allowed someone to rob her.