When roof bolts are installed by a continuous mining machine with intregal roof bolting equipment:
(a) The distance between roof bolts shall not exceed 10 feet crosswise.
(b) Roof bolts to be installed 9 feet or more apart shall be installed with a wooden crossbar at least 3 inches thick and 8 inches wide, or material which provides equivalent support.
(c) Roof bolts to be installed more than 8 feet but less than 9 feet apart shall be installed with a wooden plank at least 2 inches thick and 8 inches wide, or material which provides equivalent support.