A $1\mathrm{.}25-$in$-$diameter ASTM class $30$ gray cast iron specimen $($see Table A$-24)$ is loaded in compression and torsion. For the torsion shown, which of the following values of $P($rounded to two sig figs$)$ will cause a safety factor of $1\mathrm{.}0,$ according to the Brittle Coulomb Mohr failure criterion?

A$.86$ kip

B$.78$ kip

C$.61$ kip

D$.55$ kip