Stella Can Produce Either a Combination of 60 Silk Tulips

Stella can produce either a combination of 60 silk tulips and 85 silk leaves or a combination of 70 silk tulips and 55 silk leaves. If she now produces 60 silk tulips and 85 silk leaves, what is the opportunity cost of producing an additional 10 silk tulips?

A) 2.5 silk leaves.
B) 10 silk leaves.
C) 25 silk leaves.
D) 30 silk leaves.