Read the following context and choose the best option to answer the question.
Context: Howard pulled out his wallet from his trousers and threw a fiver onto the bar , but the barman shook his head and mouthed ' Tenner ' . Howard was silently outraged at the price of a whiskey but consoled himself with the thought that he did n't go out often , so he may as well spend up big . The whiskey sour was sharp on his throat and he almost gagged at the smell , but after the second swallow , it was n't so bad . Howard saw a shadow sliding up towards him .
Question: What is the reason the barman shook his head and mouthed tenner ?
Options: 
- None of the above choices .
 - he insisted on hearing the song Danny Boy in a tenor voice for his drink
 - He had paid too much and wanted less than a fiver .
 - a " fiver " was n't enough to pay for his liquor .


a " fiver " was n't enough to pay for his liquor .