Out of a long-term record of precipitation for four adjacent stations you find that records of one station (station D) are missing for the spring months, September, October, and November for the year 2011. For those three months the other three stations recorded the following total depth in mm.

Estimate the missing precipitation if the long-term average precipitations for the three months in all four stations are:

An alternative way of estimating a missing record is by weighting observations by the inverse square distance to the point of the missing record. If the distance of the station D from stations A, B, and C are 5 km, 1 km, and 10 km respectively, compute the missing records for the station D.