For the Box exercise check out the chapter [Using Box to Point to Data on the Heap](https://doc.rust-lang.org/book/ch15-01-box.html).
For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/ch16-03-shared-state.html) of the Rust Book.
For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/).
