Given,Bomber can destroy
bridge with two bombs.
Probability of bomb hitting, P(B)=0.4
Probability of bomb not hitting, P(NB)=0.6
4 bombs are dropped,
Given, distribution is in the form of binomial proability distribution,
Probability of bridge destroyed = (Probability only two bomb hits the bridge) + (Probability three bomb hits the bridge)(Probability four bombs hits the bridge)
Compare with given ab, we have