In arithmetic, the aditive identity says that for some number a, a + 0 = 0 + a = 0. what would be an aditive
identity in matrix arithmetic?

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

The function show two sisters' savings account and the rate at which they plan to deposit money

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?