How to use javascript promise in async and await functions?

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Javascript

Async

How to Create two async functions, where first function will wait for 10 sec and returns sum of any numbers of argument of type number(using spread operator) and second function will wait for the first function to finish and add 10 more to the return value of first function and finally returns the output.
How to resolve this using spread operator and promise
I'm new to javascript...I'm thankful for any help towards this

What I have tried:

var a=0;
setTimeout(function() { Addition(); }, 10000);
async function Addition() 
{
  for (var i=0; i < arguments.length; i++) {
  a += arguments[i];    
}
return a;
}
secondFunction();
async function secondFunction()
{
 await Addition();
 a = a + 10;
 return a;
};
 console.log(Addition(2, 3));

Here in above code I tried using async() and await(), please tell me where can I use spread operator and How to use promise in these functions here?