I have a friend in New Hampshire that owns a lawn and garden store. Let's call him Donny. Donny told me he has been selling fertilizer for $30 per bag. Due to rising costs, he recently raised his price to $35 per bag. He is concerned because he has seen a 15% drop in demand since he raised the price.

What is the price elasticity of these bags of fertilizer? Is demand elastic or inelastic? Should Donny be worried?