Sure honestly don’t know this
In this case, all letters are unique.
Start by holding the first letter:
E - XAM
E - XMA
E - MAX
E - MXA
E - AXM
E - AMX
So there are 6 combinations here.
Repeat for all 4 letters.
6 x 4 = 24
This is same as 4x3x2x1.
For 3 unique characters, it is 3x2x1.
For 5 unique characters, it is 5x4x3x2x1
And so on...
Answer: The minimum reliability for the second stage be 0.979.
Step-by-step explanation:
Since we have given that
Probability for the overall rocket reliable for a successful mission = 97%
Probability for the first stage = 99%
We need to find the minimum reliability for the second stage :
So, it becomes:
P(overall reliability) = P(first stage ) × P(second stage)

Hence, the minimum reliability for the second stage be 0.979.
Pretty sure that it is 9/7.