Probability Distribution of X; 2 erroneous transactions within 20?

A sample of 20 transactions contains 2% of errors. X denotes the number of transactions found to be in error. I m wanting to to state the probability distribution of X (incl the values of all parametres) as well as finding the probability that 2 transactions are in error.

Does anyone have an idea on how to tackle this? I m stuck with stats... 

Would really appreciate any input :)

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