Form I-864, Part 3, question 8? Part 1, question 1?

For the affidavit of support, my husband and I will be using our joint incomes. We know that for this we will need to fill out 2 forms, 1 for each of us. Which box do we check for part 1, question one? a. I am the petitioner. I filed or am filing for the immigration of my relative. d.I am the only joint sponsor or e. i am the first, or 2nd joint sponsor? and also, for part 3, question 8, i check the box that i am spnsoring the principle immigrant in part 2 above, and then do i check yes, or no? Thanks!