(a) The board may prescribe:
(1) the method and manner of making purchases and expenditures by and for the district; and
(2) all accounting and control procedures.
(b) A purchase that involves the expenditure of more than the amount provided by Section 252.021(a), Local Government Code, may be made only after advertising in the manner provided by Chapter 252 and Subchapter C, Chapter 262, Local Government Code.