Mr brown invested 12000,part is invested at 6% and the remainder at 8% .if the interest from the 6%is $230 more than the interest from the 8% investment, how much is invested at each rate

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?