In physics, these vectors are represented as `ai`, `bj` and `ck`. `a`, `b` and `c` are real numbers. `i`, `j` and `k` represent the direction in the Cartesian plane, along the axises `x`, `y` and `z` respectively. Therefore, we use the fields `i`, `j` and `k` in the structure.
Take a look how the operations `Addition` and `Subtraction` work for a 3 dimensional vector, and implement them by creating the `std::ops::Add` and `std::ops::Sub` traits.