It was my first job with a new client. The job was short (2 days only) but because the client was very slow in responding to E-Mails, it took nearly a month to finish it. The client took time ranging from few days to even a week in replying to E-Mails. That wasted mine lot of time as I was not able to work continuously and I have to setup work environment every time.
Since the contract doesn't talk about response hours limit and was fixed price, can I still ask the client for extra payment for my time wasted due to very slow response to E-Mails? Will be considered ethical or unethical? If yes how much should I increase and what reason should I give the client for that?