Hi Everyone

I am new at HTML coding. I've tried to code a calculation for a web site. My purpose is; user enter number and
chose a variable (there are 3 variable button), and when user click on "hesapla" the program should multiple the number with a constat that come from variable. But i've failed. It's basicly like this:

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<html>
<body
<p> Sayı yazın </p>
<p><input id="sayi" type="text"></p>
<p>Sınıfını Belirleyin</p>
<form>
<input type="radio" name="sinif" value="az"> Az
<br>
<input type="radio" name="sinif" value="normal"> Normal
<br>
<input type="radio" name="sinif" value="cok"> Çok
</form>
<button type="button" onclick="saatbul()">Hesapla</button>
<p id="sure"></p>
<script>
function saatbul()
{
var x=document.getElementById("sayi").value;
var y;

if (element.src.match("az"))
{
y=x*0.5;
}
if (element.src.match("normal"))
{
y=x*0.75;
}
else
{
y=x*0.95;
}
document.getElementById("sure").innerHTML=y;
}
</script>
</body>
</html>
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Could somebody help me?