1)
How did he acquire the field?
1.
Malbim (9-11): He acquired it through all 1 the Kinyanim - Kesef (like it says in this verse), and a document (verse 10).
1
Why did he say 'all'? There were only two! Malbim explains that he had witnesses on both Kinyanim, and there were two documents. However, he did not use Chazakah or Chalipin! (PF)
2)
How much money did he give?
1.
Radak citing Targum Yonasan: He gave seven Manim 1 and 10 Sela'im.
1
Rashi (Shemos 38:24): A Maneh is 25 Sela'im.
