(1) In considering whether a bargaining unit is appropriate, the board shall consider such factors as:

(a) community of interest;

(b) wages;

(c) hours;

(d) fringe benefits and other working conditions;

(e) the history of collective bargaining;

(f) common supervision;

(g) common personnel policies;

(h) extent of integration of work functions and interchange among employees affected; and,

(i) desires of the employees.