How to pronounce “sternly” in English

Behind us my own scout had come in to do the same for us.I said sternly, 'Do you know who this fellow is, Phil?' Phil had fought at the Battle of Loos, and after that earlier war had spent 15 years in the Oxfordpolice. He was affable and devoted to the College, but seemed sometimes to regret that he had ended up in an apron, dusting and washing dishes for young man