text: function addVAT(price) {
      return price + (0.2 * price);
  }
  
  function getFullName(firstname, surname) {
      return firstname + ' ' + surname;
  }
  
  function makeHalfPrice(price) {
      return (price/2);
  }
  
  function countBooks(array) {
      return (array.length);
  }
  
  function isInStock(book) {
      return (book.quantity > 0);
  }
  
  /* Put in all parameters being counted (a, b, c),
  as input into test (quantity, price, VAT)*/
  function getTotalOrderPrice(quantity, price, VAT) {
      let exVAT = quantity*price;
  // ? How do we know what 'VAT' is?  
      return exVAT + (VAT*exVAT);
  }
  
  module.exports = {
      addVAT,
      getFullName,
      makeHalfPrice,
      countBooks,
      isInStock,
      getTotalOrderPrice
  };