What kind of items require that purchase orders be placed well in advance of the time when the items are needed on the job?

Acountershaft is supported by two tapered roller bearings using indirect mounting. the radial bearing loads are 1120 lb for the left-hand bearing and 2190 lb for the right-hand bearing. the shaft rotates at 400 rpm and is to have an l10 life of 40,000 hours and an application factor of 1.4. assume ka2k 15, and find the required radial rating of each bearing