Astudy analyzed the average yearly salt intake in the united states from 2012 thru 2017. the data is summarized in the table:

year annual salt intake
(grams)
2012 3,618
2013 3,646
2014 3,680
2015 3,716
2016 3,751
2017 3,790

the study found that the data after the year 2012 can be modeled by the function f(x) = 36.4x + 3,608, where x is the number of years since 2012 and f(x) is the total amount of salt ingested in grams. describe the significance of 3,608.
the average amount of salt in grams used in 2013
the average amount of salt in grams used in 2012
an estimate of the average grams of salt used in 2013
an estimate of the average grams of salt used in 2012