If one of precisely ten men, who form a minyan, had driven to shul (the synagogue) on shabbat, is that an acceptable minyan?
I would have though not, since one is benefiting from his melacha on shabbat, but was told that either this is not called a benefit, or that one is allowed to benefit from melacha that is done by a Jew on shabbat in general, just not in the case of bishul.
Are either of those two things true?