80. The assets of a plan may be invested or loaned otherwise than as authorized by sections 65 to 73 and 77 to 79 provided:(a) that the total amount of such investments does not exceed 7% of the book value of the plan’s total assets;
(b) that such investments do not derogate from the restrictions imposed by the second paragraph of section 69;
(c) that such investments be not in real estate.