A 40 cm diameter pipe 600 m long carries 260 liters per second of water from reservoir A, discharging into two pipes each 500 m long. One pipe is 30 cm in diameter and leads to reservoir B, in which the water surface is 5 m lower than in A. If the water surface in reservoir C is 7 m lower than that at reservoir A, determine the diameter of the pipe leading to reservoir C. Use Darcy-Weisbach formula with f = 0.022.