Kirby subscribed to purchase 100 shares of stock to be issued by Globule, Inc., an already existing corporation. Globule accepted the subscription. The price set forth in the subscription agreement was $10 per share. The par value of the stock was $8 per share. When the time came for Kirby to pay the amount of his subscription, Kirby paid only $6 per share, claiming that such amount represented the fair value of the shares. Globule delivered the stock certificates to Kirby, but demanded the other $4 per share. Is Kirby liable for the other $4 per share