A company manufactures watches for which ( p = 1500 - 3x ) represents the demand function. The break-even points if the variable cost is Rs. 420 per unit and the mixed cost is Rs. 38400 are:
a) ( x = 280 ) units and ( x = 450 ) units
b) ( x = 120 ) units and ( x = 500 ) units
c) ( x = 200 ) units and ( x = 300 ) units
d) ( x = 350 ) units and ( x = 600 ) units
