many of which与of which many引导非限制性定语从句

下面哪句对? 或是两句都对?

He has a lot of books, many of which are about African Americans.

He has a lot of books, of which many are about African Americans.

两句都对。类似的使用方法如：

1. 共有500名乘客，其中有121名溺弊。

There were 500 passengers, 121 of whom drowned.

There were 500 passengers, of whom 121 drowned.

2. 我看见了3张折叠床，其中两张已有人占了。

I saw three camp beds, two of which were occupied.

I saw three camp beds, of which two were occupied.