Answer
d = 1.006 in
d = 1.25 in
n = 4.79
Work Step by Step
$\sigma = \frac{S}{n_d}=\frac{32(1000)}{\pi d^3}=\frac{25(10^3)}{2.5}\rightarrow d = 1.006$ in
Table A-17: $d=1.25$ in
Factor of safety: $n = \frac{S}{\sigma}=\frac{25(10^3}{\frac{32(1000)}{\pi (1.25)^3}}=4.79$