code question

interviewProblem.js

function remoteMathService(cb){
  var one;  
  var two;
  callOneService(function (err,num){
  	one = num;
  });	
  callTwoService(function (err, num){
  	two = num;
  });

  return cb(undefined,one + two);
}


function callOneService(cb){
	setTimeout(function (){
		return cb(undefined,1);
	},1000);
}

function callTwoService(cb){
	setTimeout(function (){
		return cb(undefined,2);
	},1500);
}


remoteMathService(function (err, answer){
	if(err) console.log("error ",err);
	if(answer !== 3){
		console.log("wrong answer",answer);
	}else{
		console.log("correct");
	}
});