Find the mean precipitation for the area shown in Fig. by Thiessen polygon method. The area is composed of a square plus an equilateral triangular plot of side 2 km. Rainfall readings are in cm at the various stations indicated. 2 km 2 km B 68 cm 10 cm Fa 15 cm 2 km 20 cm D x38 cm 2 km • Rain gauge stations 43 cm