From January 1, 2021, the price of petrol (in Rupees per litre) on $m^{\text{th}}$ day of the year is $80 + 0.1m$ , where $m = 1, 2, 3, \dots, 100$ and thereafter remains constant. On the other hand, the price of diesel (in Rupees per litre) on $n^{\text{th}}$ day of 2021 is $69 + 0.15n$ for any $n$ . On which date in the year 2021 are the prices of these two fuels equal ?