25 1) Estimate the grade at the point B from A and D using kriging when the variogram model for grade is spherical with parameters Co-50, C-50, a-500m and Z(A)=10% and z(D)=16%. A 100m B-? 400m D 25 2) The following figure shows the locations for which thickness is measured in a mineral deposit. The mean and variance of thickness are 3m and 20 respectively. The variogram model of the thickness is linear. When the density is 2.4t/m, calculate the tonnage and construct 95% confidence interval for the true tonnage. +0.0609) N > N H(I)-0.7652*, F(II)-0.5213*/ Var(1) -2H(0.5 1,0.5*)-F(I.) = F(I.) 112.5 97.5 62.5 87.5 87.5 253) Define estimation variance, extension variance, dispersion variance and kriging variance.