(a) The state of Rhode Island is hereby authorized to exclude from wages, payments made under a written plan or system of sick leave. The written plan shall be established pursuant to this authority by the department of administration and must contain at least the following:
(1) A method of determining sick pay eligibility;
(2) A method of determining the duration of sick pay payment;
(3) A method of determining the minimum amount of sick pay payment.
(b) This plan shall be established by July 1, 1982.