In a gas chromatography (GC) separation involving four components, it was discovered that all four components, A, B, C and D, separate cleanly at 80 ℃. At this temperature, A and B have fairly short retention times, but components C and D have very long retention times. It was also discovered that C and D separate cleanly at 150 ℃ while that A and B do not. Suggest a temperature program that would separate all four in a reasonable time and explain why it would work.