$5.$ A polymerization plant produces $10,000$ tons of polypropylene annually. If the conversion rate of propylene to polypropylene is $85\%,$ how many tons of propylene are required for the production?

$6.$ In a catalytic reforming process, $1,000$ barrels of low$-$octane gasoline are converted into $800$ barrels of high$-$octane gasoline and $100$ barrels of other products. What is the conversion efficiency of low$-$octane gasoline to high$-$octane gasoline?