A manager has the option of purchasing one, two, or three machines. Fixed costs and range of output are as follows: $(15$points $)\backslash$ table $[[$ Number of Machines,Total Annual fixed cost $($ $ $),$ Corresponding range of output $],[1,9,600,0$to $300],[2,15,000,301$to $600],[3,20,000,601$to $900]]$Variable cost is $ $10$per unit, and revenue is $ $40$per unit. I $)$Determine the break $-$ even point $($ if any $)$for each range. II $)$If projected annual demand is between $580$and $660$units$,$ how many machines should the manager purchase?