Selecting the first JSON result after predicate - json

Question

I'm trying to write a JSON path that contains a predicate not specific enough to select a single element, yet I want to force the result to be the first one. I would like to have it done using the path only (not as part of the C# code later).
The following path returns the first book, which I expected: $.book[0]
The following path returns exactly two books with price > 0, which I expected: $.book[?(#.price>20)]
Now, I would like to return the first element from the result. I was hoping for this to work, but it doesn't. Somehow this does not work at all:
$.book[?(#.price>20)][0]
I am using .NET and Json.NET library, but I am open to any other.
The example JSON is as follows:
{
"book":[
{
"title":"Beginning JSON",
"author":"Ben Smith",
"price":49.99
},
{
"title":"JSON at Work",
"author":"Tom Marrs",
"price":29.99
},
{
"title":"Learn JSON in a DAY",
"author":"Acodemy",
"price":8.99
},
{
"title":"JSON: Questions and Answers",
"author":"George Duckett",
"price":6.00
}
]
}