2.By Bayes formaula the probability that 2A are produced by 3 transmiter equals to the probability that 3 transmiter made 2 A multiplied by the probability that 2 signals were made by 3 transmiter divided by the probability that we recieved 2 A
Probability that 3rd transmiter made 2 A is \(\frac{3}{5}*\frac{3}{5}=\frac{9}{25}\)
Probability that 2 signals were made by 3rd transmitter is \(\frac{2}{10}*\frac{2}{10}=\frac{1}{25}\)
Probability to receive 2A is equal to the sum of product of corresponding probabilities of making A by some particular transmitter and probabilities that this transmitter sent a signal:
\(\frac{3}{5}*\frac{3}{5}*\frac{2}{10}*\frac{2}{10}+\frac{2}{3}*\frac{2}{3}*\frac{3}{10}*\frac{3}{10}+\frac{3}{7}*\frac{3}{7}*\frac{5}{10}*\frac{5}{10}+2*\frac{3}{5}*\frac{2}{3}*\frac{2}{10}*\frac{3}{10}+2*\frac{3}{5}*\frac{3}{7}*\frac{2}{10}*\frac{5}{10}+2*\frac{2}{3}*\frac{3}{7}*\frac{3}{10}*\frac{5}{10}=\frac{9}{625}+\frac{1}{25}+\frac{9}{196}+\frac{6}{125}+\frac{9}{175}+\frac{3}{35}=\frac{34969}{122500}\)
Finally, we have
\(\frac{\frac{9}{25}*\frac{1}{25}}{\frac{34969}{122500}}=\frac{9*196}{34969}=\frac{1764}{34969}\)
Actually, there should be something wrong in my solution)))