If I sell multiple used cars during the year some for loss some for gain are they kept track of individually or total for the year?

For example if I sell two cars for a profit but two cars at a loss in my taxed on the bottom line for all four cars or am I taxed on the ones with profit and not taxed on the ones that I had a loss. A side question with that if I have a total gain at the end of the year from those sales does that profit go into my overall income and count under the earned income credit guidelines?