The Texas park development bonds interest and sinking fund, referred to as the "interest and sinking fund," is created to be used exclusively for:

1. (1) paying the principal of Texas Park Development Bonds as they mature;
2. (2) paying the interest on the bonds as it comes due; and
3. (3) paying exchange and collection charges in connection with the bonds.

Acts 1975, 64th Leg., p. 1405, ch. 545, Sec. 1, eff. Sept. 1, 1975.