)the class boundary between two consecutive classes is
a. the difference of their lower class limits divided by 2
b. the average of their upper class limits
c. the difference of their class midpoints divided by 2
d. the middle point between them
e. the difference of their upper class limits divided 2
f. the average of their lower class limits
g. none of the above.

State one method by which you can recognize a perfect square trinomial.

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1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?