(a) Investment by participant.--All contributions, interest and investment earnings shall be invested based on a participant’s investment allocation choices, provided that the board may provide for a default investment option. All investment allocation choices shall be credited proportionally between participant contributions and employer defined contributions. Each participant shall be credited individually with the amount of contributions, interest and investment earnings.

(b) Investment of contributions made by entities other than the Commonwealth.--Investment of contributions by any corporation, institution, insurance company, custodial bank or other entity that the board has approved shall not be unreasonably delayed, and in no case may the investment of contributions be delayed more than 30 days from the date of payroll deduction or the date voluntary contributions are made to the date that funds are invested. Any interest earned on the funds pending investment shall be used to pay administrative fees, costs and expenses of the plan.