For $N-80,9^{\frac{5}{8}}$ in$.$ API Buttress thread connections calculate" $($i$)$ pipe thread strength, $($ii$)$ coupling $($regular$)$ thread strength, $($iii$)$ cou pling 'special clearance' thread strength. Using Let $=4\mathrm{.}041in.$ plus the additional manufacturer's data: $d_{co}=10\mathrm{.}625in.($regular$),d_c=10\mathrm{.}125in.($special clearance$),d_{\text{r}\text{o}\text{o}\text{t}}=9\mathrm{.}4517in.$

Assume that ${}_{up}={}_{uc}=100,000$psi