Two things happen: (i) the price of corn decreases; (ii) the price of crude oil decreases.
a) Qethanol ↑ and we can't tell what happens to Pethanol.
b) Qethanol ↓ and we can't tell what happens to Pethanol.
c) Pethanol ↑ and we can't tell what happens to Qethanol.
d) Pethanol ↓ and we can't tell what happens to Qethanol.