Completing A Program..

Hi all,

I'm new to Java and wondering if anyone can give me any pointers into this program I'm trying to complete.

Its using if..else structures.

if (the current bid is less than £10)
increase the bid by £0.10
else
if (the current bid is at least £10 but less than £100)
increase the bid by £0.50
else
if (the current bid is at least £100 but less than £1000)
increase the bid by £1.00
else
increase the bid by £10.00

<HEAD>
<TITLE>Bid Increases</TITLE>
</HEAD>
<BODY>
<SCRIPT LANGUAGE = "JavaScript">

var currentPrice;
var bidIncrement;
var newPrice;

currentPrice = window.prompt('Please enter the current bid price', '');

document.write ('The new bid is £' + newPrice);

</SCRIPT>
</BODY>
</HTML>

I really cannot work out how to complete the program.

Any help appreciated!!