I wasn't sure how to order things, so I decided to write directly on top of your screenshots. Have a look at the three attachments. Two of which are correct. There is one incorrect answer though you're fairly close.
The answer would be 24j+30+24j which is 48j+30
<h3>
Answer: 21600 </h3>
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Explanation:
There are 6 letters to pick from {A,B,C,D,E,F} and we have two slots to fill, where no repeats are allowed. This means we have 6*5 = 30 different ways to pick two letters.
There are 10 digits to pick from {0,1,2,...,9} and there are 3 slots to fill. This gives 10*9*8 = 720 different permutations for this portion.
Overall, we have 30*720 = 21600 different serial numbers possible.
Three hundred ninety six divided by twenty four = 16.5
Answer:
1 option or last option are the best choices sorry if I'm wrong.
