B. 1:5
Feedback Cost of 1 litre of water = Rs.0 = cheaper quantity.
Cost of 1 litre of juice = Rs.24 = dearer quantity.
And, the mean price = m = Rs.20
Therefore, (Cheaper quantity) : (Dearer quantity) = (d - m) : (m - c) = 4:20 = 1:5
Hence, the required answer is 1:5.