= Solution
The integer molecular mass of the stated isotopologue is
$$
m=(12+1+3\cdot35)u=118u\simeq1.95944\times10^{-25}\ \mathrm{kg}.
$$
Take $p^\circ=1\ \mathrm{bar}=10^5\ \mathrm{Pa}$, the recommended <standard pressure>.<IUPAC Compendium of Chemical Terminology, fifth edition (Gold Book)>[Entry S05921, <standard pressure>: recommended value 100000 Pa]{ref}
At $298\ \mathrm K$, the <thermal de Broglie wavelength> is $\Lambda\simeq9.3100\times10^{-12}\ \mathrm m$. The result of part (a) gives
$$
S^\circ_{\rm trans,m}
=R\left[\ln\frac{k_{\rm B}(298)}{(10^5)\Lambda^3}+\frac52\right]
\simeq\boxed{168.34\ \mathrm{J\,K^{-1}\,mol^{-1}}.}
$$
If $1\ \mathrm{atm}$ is used instead, the result decreases by $R\ln(1.01325)\simeq0.1094\ \mathrm{J\,K^{-1}\,mol^{-1}}$, giving $168.23$ in the same units. Specifying the <pressure> removes that small convention dependence.
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