I'm sorry; (it's) inexcusable; thank you very much (for help, etc.)
I'm sorry; (it's) inexcusable; I feel regretful; thank you very much (for help, etc.)
I'm sorry; (it's) inexcusable; thank you very much (for help, etc.)
poor excuse (of a); nearly non-existent; barely sufficient; token (effort, etc.); symbolic
I'm sorry; (it's) inexcusable