prijs update niet in chrome

                <form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
                	<select name="type" class="grant-me">
                    	<option value="1.00" onclick="updateAmount('1.00')">Cub Sandwich $1,00</option>
                        <option value="2.50" onclick="updateAmount('2.50')">Antelope $2,50</option>
                        <option value="5.00" onclick="updateAmount('5.00')">Whole zebra $5,00</option>
                    </select>
                    
                    <input type="hidden" name="cmd" value="_donations">
                    <input type="hidden" name="business" value="claudiabussemaker@gmail.com">
                    <input type="hidden" name="lc" value="NL">
                    <input type="hidden" name="item_name" value="The Lion King Collector">
                    <input type="hidden" name="item_number" value="TLKC">
                    <input type="hidden" name="amount" id="amount" value="1.00">
                    <input type="hidden" name="currency_code" value="USD">
                    <input type="hidden" name="no_note" value="0">
                    <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
                    <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal, de veilige en complete manier van online betalen.">
                    <img alt="" border="0" src="https://www.paypalobjects.com/nl_NL/i/scr/pixel.gif" width="1" height="1">
                </form>

                <script language="javascript">
				function updateAmount(amount){
					document.getElementById('amount').value = amount;
				}
				</script> 

<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
                	<select name="type" class="grant-me">
                    	<option value="1.00" onclick="updateAmount('1.00')">Cub Sandwich $1,00</option>
                        <option value="2.50" onclick="updateAmount('2.50')">Antelope $2,50</option>
                        <option value="5.00" onclick="updateAmount('5.00')">Whole zebra $5,00</option>
                    </select>
 
                    <input type="hidden" name="cmd" value="_donations">
                    <input type="hidden" name="business" value="claudiabussemaker@gmail.com">
                    <input type="hidden" name="lc" value="NL">
                    <input type="hidden" name="item_name" value="The Lion King Collector">
                    <input type="hidden" name="item_number" value="TLKC">
                    <input type="hidden" name="amount" id="amount" value="1.00">
                    <input type="hidden" name="currency_code" value="USD">
                    <input type="hidden" name="no_note" value="0">
                    <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
                    <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal, de veilige en complete manier van online betalen.">
                    <img alt="" border="0" src="https://www.paypalobjects.com/nl_NL/i/scr/pixel.gif" width="1" height="1">
                </form>
 
                <script language="javascript">
				function updateAmount(amount){
					document.getElementById('amount').value = amount;
				}
				</script>