what size propane tank do i need to run a 16kw generator for 5 days?

generac air cooled 15/16 kw ....owners manual says natural gas = 173@half load, 245@full load and propane=1.59/59@half load,2.51/92@full load...nat gas is in cubic ft,lp is in gallons per hour/cubic ft....so with lp(propane) how big of a tank(gallons) do i need to run at half load for 5 days?