(b) An inmate identified in subdivision (a) of this section who is serving a sentence for any Class A-II through Class E drug offense may earn supplemental merit time in the amount of an additional one-sixth of the minimum period of the sentence imposed for the drug felony if he or she has either:

1. (1) completed two or more of the four possible merit program objectives listed in section 280.2(d) of this Title:

   1. (i) earned a general equivalency diploma (G.E.D.);
   2. (ii) received an alcohol and substance abuse treatment certificate;
   3. (iii) received a vocational trade certificate following at least six months of programming in that program; or
   4. (iv) performed 400 hours or more of service as part of a community work crew/outside assignment; or
2. (2) completed one of the four and also successfully maintained employment in a work release program or other continuous temporary release program for a period of not less than three months.