Teaser 2877: Four steadings and a numeral

From The Sunday Times, 12th November 2017 [link]

Farmers Al, Bo, Cy and Di have different double-digit numbers of sheep kept in their respective steadings. Al has the fewest and his number of sheep is a certain fraction of Bo’s number of sheep. Also, Bo’s number of sheep is that same fraction of Cy’s number, and Cy’s number is that same fraction of Di’s.

If I told you the total of Bo’s number of sheep added to Cy’s, then you would be unable to work out all their numbers of sheep. Similarly, if instead I told you just Bo’s number of sheep, then you would be unable to work out all the other numbers.

What (in the order Al, Bo, Cy, Di) are their numbers of sheep?

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