1.  Average final compensation.  The service retirement benefit of a person who returns to employment with that person's former employer or any other employer whose employees are covered by this article or chapter 423, subchapter V, article 3‑A, after having been the recipient of a disability retirement benefit, shall be computed in its entirety using the average final compensation as defined by section 17001, subsection 4, on the date of that person's termination from service immediately before becoming the recipient of a service retirement benefit.  

2.  Cost of benefits.  The cost of benefits based upon service credits earned before and during disability must be charged to the Retirement Allowance Fund. The cost of benefits based upon service credits earned after becoming reemployed must be charged to the account of the employer through whom the service credits were earned.  

3.  Special plans.  The service credits earned after return to employment by a person who was employed under a special plan before becoming the recipient of a disability retirement benefit shall be credited toward completing the service requirements for retirement under that special plan. As used in this section, unless the context otherwise indicates, "special plan" means any of the retirement programs in section 17851, subsections 4 to 11 or section 18453, subsections 2 to 9.