Chris and Diane each bought 15 ounces of coffee in a 20-ounce cup. Chris drank 4 ounces of his coffee and then added 4 ounces of cream. Diane added 4 ounces of cream, stirred the coffee well, and then drank 4 ounces. What is the resulting ratio of the amount of cream in Diane's coffee to that in Chris's coffee?