## Molecules Cells

### Instructions

Create two functions which accept a `string`, and return a `string`:

- `RNA`: that converts a DNA strand into its compliment RNA strand.
- `DNA`: that converts an RNA strand into its compliment DNA strand.

Compliments:
```
DNA | RNA
 G  -  C
 C  -  G
 T  -  A
 A  -  U
```

Each strand must be represented as upper case `string`, without spaces, eg: `"ATCG"` is a valid DNA strand.
