One day, River writes down the numbers 1, 2,, 999 What is the sum of all the digits that River wrote down? And what is the number of all the digits River wrote down

Me with this one question, and i'll upvote the brainliest answer

The monetary value earned for selling goods or services to customers is called a.) revenue b.) assets c.) money d.) accounting

Select the margin of error that corresponds to the sample mean that corresponds to each population: a population mean of 360, a standard deviation of 4, and a margin of error of 2.5%