(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.