1. find the following probability

A train of n wagons transports hazardous materials. Each wagon, and independently
from the others, has a probability p to be defective. Prior to the train’s departure all
wagons are examined by two inspectors who do not exchange their inspection’s results during the control. We assume that each inspector will detect a default on a given wagon (if any) with probability r. One default is enough to delay the train’s departure(for repair). Compute the following probabilities.

that the train’s departure will be delayed?

do I use the conditional prob formula here, P(A|B) where B is the prob that the inspector will find a default, and A is the train will be delayed?
but how do I find the prob of A and B?

2. Originally Posted by wopashui
A train of n wagons transports hazardous materials. Each wagon, and independently
from the others, has a probability p to be defective. Prior to the train’s departure all
wagons are examined by two inspectors who do not exchange their inspection’s results during the control. We assume that each inspector will detect a default on a given wagon (if any) with probability r. One default is enough to delay the train’s departure(for repair). Compute the following probabilities.

that the train’s departure will be delayed?

do I use the conditional prob formula here, P(A|B) where B is the prob that the inspector will find a default, and A is the train will be delayed?
but how do I find the prob of A and B?

you should have checked a few threads before posting this.. Someone has already asked the same question just before you did..even his/her title says train containing hazardous material!!