The probability of safe arrival of the ship is 1/5
Using Bernoulli’s Trial we have,
P(Success=x) \(=n_{C_x}.p^x.q^{(n-x)}\)
x = 0, 1, 2, ………n and q = (1 - p), n = 5
p = 1/5 , q = 4/5
Probability of safe arrival of at least 3 ships is = P(3)+P(4)+P(5)