Your linked audio exports in MP as either a mix or individual track mp3, using the drop-down menu that appears when clicking the caret to the right of the Save toolbar button.

In order to save the project, ignore my earlier instruction. Follow this path to save to Google Drive.
Click to enlarge.
Then in Google Drive right-click on each item...

For each item, click SHARE | SHARE and change "restricted" to "anyone with link can view." Then COPY. Post the two copied links here.
Then someone can download both the control mpdp file and the folder containing the source files.
Or simply Export As Audio File (from the above menu), and select mp3. That should mix the tracks and result in an mp3. Does here.