In this task, you need to provide the correct option for a given problem on probability from the provided options.

Example Input: Problem: in how many ways 7 boys and 7 girls can be seated in a row so that boys and girls are alternate ? 
Options: a ) 50803200 , b ) 50328000 , c ) 50003280 , d ) 50703200 , e ) 50603200
Example Output: a

Example Input: Problem: x , y , and z are all unique numbers . if x is chosen randomly from the set { 8 , 9 , 10 , 11 } and y and z are chosen randomly from the set { 20 , 21 , 22 , 23 } , what is the probability that x and y are prime and z is not ? 
Options: a ) 1 / 16 , b ) 3 / 11 , c ) 13 / 20 , d ) 3 / 10 , e ) 1 / 10
Example Output: a

Example Input: Problem: if a coin is flipped , the probability that the coin will land tails is 1 / 2 . if the coin is flipped 3 times , what is the probability that it will land tails up on the first flip and not on the last 2 flips ? 
Options: a ) 1 / 8 , b ) 1 / 4 , c ) 1 / 3 , d ) 1 / 2 , e ) 3 / 4
Example Output:
a