This paper investigates a Supply Chain System for deteriorating items in which a supplier supplies a manufacturer with raw material, and the manufacturer produces the finished goods. Demand rate is assumed to be time-sensitive in nature (Trapezoidal type), which allows three-phase variation in demand, and production rate is demand dependent. Our adoption of trapezoidal type demand reflects a real market demand for newly launched product. We show that the total cost function is convex. With the convexity, a simple solution algorithm is presented to determine the optimal order quantity and optimal cycle time of the total cost function. Numerical examples are given and the results are discussed.