I'll give brainliest to whoever answers the question correctly All of the following would make a formal proof incomplete except what?

A.) Errors in logic
B.) A lack of justifications
C.) Incomplete sentences
D.) Incorrect reasons for statements

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?