How to access mapped objects in another function in ReactJS ?

import React, { Component } from "react";

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      books: [
        { title: "Book Title 1", USD: 10 },
        { title: "Book Title 2", USD: 20 },
      ],
    };
  }

  // We want to pass books object in this function
  // and return Rupees value
  usdToRupees = (book) => {
    return book.USD * 75;
  };

  render() {
    return (
      <div>
        {this.state.books &&
          this.state.books.map((book) => {
            return (
              <div>
                <h2>{book.title}</h2>

                
<p>USD = {book.USD}</p>


                {/* We are passing book object to the function */}
                
<p>Rupees = {this.usdToRupees(book)}</p>


                <hr></hr>
              </div>
            );
          })}
      </div>
    );
  }
}

export default App;