When a party to a contract does not meet its performance obligation despite having no legal excuse not to perform what does that constitute?

In what position does the law seek to put the innocent party when the other party does not perform?

What is the monetary form of contractual remedy called?

You agree to paint my house for $500. You don't show up and I have to pay another painter $900 to do the job.

a) What is the appropriate measure of compensatory damages?

b) How would your answer change (if at all) if I prepaid you for the job?

c) Can you name some incidental damages I might have incurred due to your breach?