Problem 9 Continuing the previous question: Find an example where A is decidable, B is regular, but A/B is not decidable. (For this, I recommend using the idea of "history strings" from Chapter 5.) Problem 9 Continuing the previous question: Find an example where A is decidable, B is regular, but A/B is not decidable. (For this, I recommend using the idea of "history strings" from Chapter 5.)