(3) Precipitation station X was inoperative for part of a month during which a storm occurred. The respective storm at six surrounding stations A, B, C, D, E, and F were 95, 78, 72, 110,63. 88mm. The normal annual precipitation amounts at X, A, B, C, D, E, and F, are, respectively, 800, 1000, 877, 841, 1080, 650, and 952mm. Estimate the storm precipitation for station X with the following to methods: a) station average method, b) Normal ratio method; The result of which method is more reliable and why? c) Moreover, by employing the result of reliable precipitation value from the previous stage for station X, for a 5% error in the estimation of the mean rainfall, calculate the optimum number of stations in the catchment