Physics · Hydrology

A catchment area has six rain gauge stations. In a given year, the annual rainfall recorded by the gauges is as follows: Station A: 82.6 cm, B: 102.9 cm, C: 180.3 cm, D: 110.3 cm, E: 98.8 cm, F: 136.7 cm. For an allowable error of 10% in the estimation of the mean rainfall, what is the optimum number of stations required in the catchment? (Given: Mean rainfall P = 118.6 cm, standard deviation σn-1 = 35.04, and error ε = 10%)