it may be a simplistic approach but if 150mt @66% and $83pt = $2.82 then every 50mt = .96c, so 200mt = $3.78 and 250mt = $4.74, and so on and so forth.
#remembering in your question you only changed the tonnage not the grade or the spot price.
PLV Price at posting:
51.8¢ Sentiment: LT Buy Disclosure: Held