A catchment may be idealized as a circle of radius 30 km. There are five rain gauges, one at the center of the catchment and four on the boundary (equi-spaced), as shown in the figure (not to scale).

The annual rainfall recorded at these gauges in a particular year are given below.

$$ \begin{array}{|l|l|l|l|l|l|} \hline \text { Gauge } & \mathrm{G}_1 & \mathrm{G}_2 & \mathrm{G}_3 & \mathrm{G}_4 & \mathrm{G}_5 \\ \hline \text { Rainfall }(\mathrm{mm}) & 910 & 930 & 925 & 895 & 905 \\ \hline \end{array} $$

Using the Thiessen polygon method, what is the average rainfall (in mm, rounded off to two decimal places) over the catchment in that year? ________

A catchment is idealized as a 25 km × 25 km square. It has five rain gauges, one at each corner and one at the center, as shown in the figure. During a month, the precipitation at these gauges is measured as G₁ = 300 mm, G₂ = 285 mm, G₃ = 272 mm, G₄ = 290 mm and G₅ = 288 mm. The average precipitation (in mm, up to one decimal place) over the catchment during this month by using the Thiessen polygon method is_______ .

In a catchment, there are four rain-gauge stations, P, Q, R, and S. Normal annual precipitation values at these stations are 780 mm, 850 mm, 920 mm, and 980 mm, respectively. In the year 2013, stations Q, R, and S, were operative but P was not. Using the normal ratio method, the precipitation at station P for the year 2013 has been estimated as 860 mm. If the observed precipitation at stations Q and R for the year 2013 were 930 mm and 1010 mm, respectively; what was the observed precipitation (in mm) at station S for that year?