Cant solve a small js challenge

So I was going through code wars and I was trying to solve a simple js program given by the site .It goes like this ;
`function multiply(a,b)
{
a*b;
}`
my intial answer was
`function multiply(a,b)
{
var product=a*b;
return product;
}
var answer=multiply(10,10);
document.write(answer);`
But the site throws a bunch of errors ,what could I be doing wrong?

Also in #JavaScript _↴