thermal prices for different cal value

Anyone know what discount 5700Kcal/kg attracts compared to 5800

from ann:

Potential for Further Yield Increases
The analysis indicated that if the average gross energy is reduced to 5,700Kcal/kg from
5,800Kcal/kg the result would be a further 7% improvement in the clean coal yield from 56% to
63%. This increase in yield would result in a significant addition to the saleable coal reserves and
clean coal production rate on Vista.