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Answer with explanation:</h2>
Given : A standardized exam's scores are normally distributed.
Mean test score : 
Standard deviation : 
Let x be the random variable that represents the scores of students .
z-score : 
We know that generally , z-scores lower than -1.96 or higher than 1.96 are considered unusual .
For x= 1900

Since it lies between -1.96 and 1.96 , thus it is not unusual.
For x= 1240

Since it lies between -1.96 and 1.96 , thus it is not unusual.
For x= 2190

Since it is greater than 1.96 , thus it is unusual.
For x= 1240

Since it lies between -1.96 and 1.96 , thus it is not unusual.
Answer:
Answer in pictures attached.
Step-by-step explanation:
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