Calling a Variable from another Script Beginner Problem

Hello, I have a Countdown Timer running to zero and Coins that should give +5 Seconds every time I collect one of them. The Countdown Script is running and the Trigger works, but how do I get to run the variable “BonusTime” from the Script “CountdownScript”?

function OnTriggerEnter(){
 BonusTime+= 5.0; }

Thanks in advance!

gameObject.GetComponent(“CountdownScript”).BonusTime+= 5.0;