What is the ruling on one who had intercourse with his wife during Ramadan, being ignorant of its prohibition, and what is the ruling on silent and audible prayer?

Sexual intercourse during the daytime in Ramadan is forbidden, and expiation (kaffara) is obligatory for whoever commits it intentionally, knowing the ruling, or being ignorant due to their own negligence. As for someone new to Islam or one who grew up in a remote desert far from knowledge and religion, there is no expiation for them. What nullifies the expiation is ignorance of the ruling concerning intercourse itself, not ignorance of the obligation of expiation.