Answer
The price will decrease by 20%.
Work Step by Step
$\Delta\ qty=\Delta\ price\times E_d$
$10=\Delta\ price\times0.5$
$10\div0.5=\Delta\ price\times0.5\div0.5$
$20=\Delta\ price$
The price will decrease by 20% because of the increased quantity.
Because the price elasticity is 0, the supply curve is vertical, meaning the entire crop will sell at the new price.
