First mix varieties  $A\&C$   in a ratio to get a mixture at the cost Rs. 141 per litre.

Applying Alligation:

Now mix varieties  $A\&B$   to get a mixture at the cost of Rs. 141 per litre.

So, A: C in ratio 11: 7 and A: B in ratio 1: 7.The required ratio A: B: C = 11: 77: 7. Hence option (c).

2nd method:- By, observation, 141 is nearest to B (144) then A(120) and then C(174). When we mix all three then highest contribution will be according the above, i.e  $B\to A\to C$ , Now only option (c).