A rectangular room with floor dimensions $38\mathrm{.}2m$ and $19\mathrm{.}5m$ is excavated at a depth to the roof of $130m.$ The density of the overburden is $2200k\frac{g}{m^3}.$ The roof of the room is supported by $28$ identical pillars each carrying the same load. Each pillar an area of $1\mathrm{.}36m^2$ and is made of rock with unconfined compressive strength $92\mathrm{.}5$MPa. Soon after completion, terrorists begin to destroy the pillars one by one. What's is the greatest number of pillars that can be destroyed without causing the roof to collapse? $($Assume that the pillars are destroyed from all parts of the room, so that the remaining pillars span regions of the roof over which the roof rock is competent$)$