Cov kabmob yog ib feem tseem ceeb ntawm cov tshuab thiab khoom siv niaj hnub no.
Nws lub luag haujlwm tseem ceeb yog txhawb nqa lub cev sib hloov lub cev, txo kev sib txhuam coefficient thaum nws txav mus los, thiab xyuas kom nws qhov kev sib hloov raug (raug).
