sat II question

<p>im planning on taking ushistory and chem in may and math 2 in june. however this will cost me both my fee waivers so i want to retake history and chem in june if i dont do so great. the thing is, i wont know my scores until late may. should i sign up for all 3 tests in june, and choose the ones i want to do? or just math 2 and during the test add the tests i want? will it cost me to do that since i used my waiver already? thanks</p>