60 kg @ 30.50 Rs/kg --> 1830 Rs
80 kg @ 32.50 Rs/lg --> 2,600 Rs
So, in total we have 140 kg sugar for a cost of 4430 Rs
20% 0f 4430 Rs is 886 Rs
So, selling price needs to be 4430 + 886 = 5316 Rs for 140 kg
5316/140 = 37.9714
So, Karan should sell his sugar mix at a selling price of 38 Rs/kg to ensure a profit of 20 %