Using Prototypes to define the Props you expect - issues

I don’t understand. What am I missing?

const Items = (props) => {
  return <h1>Current Quantity of Items in Cart: {props.quantity}</h1>
};

// change code below this line
Items.propTypes = {
quantity: propTypes.number.isRequired
}
// change code above this line

Items.defaultProps = {
  quantity: 0
};

class ShoppingCart extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <Items />
  }
};
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