A cylindrical core has a bulk volume of $26\mathrm{.}2c{m}^3$ and an effective pore volume $=7\mathrm{.}7c{m}^3.$ The pore volume was occupied by $0\mathrm{.}77c{m}^3$ oil, water and gas are equal in volumes. Determine $.$the grain volume? express your answer in $c{m}^3$