In a certain desert environment, there are a lot of small rodents. there also happen to be lots of snakes that feed on the rodents. the ratio or rodents to rodent eating snakes are 13 to 13. if there are 4,000 snakes in the area, about how many rodents are there?

Consider u = {x|x is a negative real number}which is an empty set? o {x|x eu and x has a negative cube root}o {x|x eu and x has a negative square root}{x|x eu and x is equal to the product of a positive number and -1}{x|x eu and x is equal to the sum of one negative and one positive number?