let library = [ { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254, totalCopies: 5, inStock: 2 }, { author: 'Walter Isaacson', title: 'Steve Jobs', libraryID: 4264, totalCopies: 2, inStock: 3 }, { author: 'Dale Carnegie', title: 'How to Win Friends and Influence People', libraryID: 3245, totalCopies: 2, inStock: 1 }, { author: 'Peter Thiel', title: 'Zero to One', libraryID: 4264, totalCopies: 6, inStock: 0 }, ]
//use an array method to determine how many books the library has in total