Hello dear members of the Forum...

Would you kindly tell me the appropriate verb forms to fill the gaps (in the following sentence) with?
-
I ______ (a. save up, b. am saving up) because I _______ (a. am going, b. go) abroad in July. I chose
'b' - 'am saving up' (for the first blank) and
'a' - 'am going' (for the second), and the site on which that is given marked me 'correct'. But I'd like to ask you whether or not I can use
'a' - 'save up' and
'b' - 'go' for the gaps, please. I'm asking this to you because 'present simple' is also used for things that happen in the future.
Thank you all.