Changamoto ni nyingi na sababu zinarange sanaa, always be prepared kwa surprises. Mf. uko zako kazini fundi amekuhakikishia amepiga mahesabu sawa. Ghalfa unadaiwa material ya kama laki kadhaa fundi alisahau, halafu unatakiwa ununue sasa ili kazi iendelee. Kuna yule hakwambii estimates vizuri ili tu umpe kazi, au fundi kaumia vibaya kisa tu hakuvaa tu protective gears za kawaida tu na uliwanunulia.