Why did you draw a sign on the sand?<br/><span style="color:#ff0000;">a-That was so that John could find us.<br/> b-That was for John to find us.</span><br/><br/> Do (a) and (b) work in these contexts?<br/> The idea is to mention the intention behind an act.<br/><br/> They seem OK to me. One could use <span style="color:#ff0000;">'it'</span> instead of<span style="color:#ff0000;"> 'that</span>'.<br/><br/> Many thanks.