Let's say I store bank accounts information in an immutable `Map`: 

```
val m = Map("Mark" -> 100, "Jonathan" -> 350, "Bob" -> 65)

```

and I want to withdraw, say, $50 from Mark's account. I can do it as follows: 

```
val m2 = m + ("Mark" -> (m("Mark") - 50))

```

But this code seems ugly to me. Is there better way to write this?