A plant manufactures compressors at the rate of N units/day. The daily fixed charges are Rs. 20000 and the variable cost per compressor is Rs. 500 + 0.2 N$^{1.3}$. The selling price per compressor is Rs1000. The number of compressors to br manufactured, to the nearest integer, in order to maximize the daily profit is $\_\_\_\_\_\_\_$