I'm trying to match the following cases and pull the number value:

```
"b 30.00"
"bill 30.00"
"bill 30"
"b 30"

```

I've tried: 

```
var regex = new Regex("^b(?-i:ill)?$ ^$?d+(.d{2})?$", RegexOptions.IgnoreCase);

```

However, this doesn't seem to return a match, and I'm not sure how to pull the digit.