A dairy has ten fermentation tanks for the production of yoghurt. The yogurt from the two most recent tanks (type A) contains, on average, 2.5 lumps per litre. Three tanks of type B average 4 lumps per litre, and five of type C averages 6 lumps per litre.
In a jar containing one liter of unlabeled yogurt, there are 3 lumps. Calculate the probability that another jar from the same series (thus containing yogurt from the same vat) contains 4 lumps.
(This is a question relating to a chapter on discrete distributions; thus the distribution should be one of the following : {Bernoulli, uniform, binomial, geometric, negative binomial, hypergeometric or Poisson}, or maybe it is solvable by elementary probability rules and theorems.)