Please show all stepts necessary

Two $18-$m diameter water tanks are placed on the ground surface. The tanks have a induced stress overlap at Point A and the design specifications stipulate a maximum induced stress$-$to$-$bearing pressure ratio of $0\mathrm{.}1$ for each tank at depths of $10m,20m,$ and $30m$ below Point $A.$ Determine the minimum distances between the tanks based on these calculations.