What Will the Browser Display If the Following Script Is

What will the browser display if the following script is executed and the user enters 5 at both prompts
< script type = "text/javascript" >
< !--
Var firstNumber = window.prompt( "Enter an integer", "0" ) ;
Var secondNumber= window.prompt( "Enter an integer", "0" ) ;
Var thirdNumber;
ThirdNumber = firstNumber + secondNumber;
Document.write( thirdNumber ) ;
//-- >
< /script >

A) nothing
B) 0
C) 10
D) 55