a. The board of adjustment shall render a decision not later than 120 days after the date (1) an appeal is taken from the decision of an administrative officer or (2) the submission of a complete application for development to the board of adjustment pursuant to section 59b. of this act.
b. Failure of the board to render a decision within such 120-day period or within such further time as may be consented to by the applicant, shall constitute a decision favorable to the applicant.