Tony is a wheat farmer - but also spends part of his day teaching guitar lessons. Due to the popularity of his local country western band - Farmer Tony has more students requesting lessons than he has time to instruct them if he is also to maintain his farming business. Farmer Tony charges $25 an hour for his guitar lessons. One spring day - he spends 10 hours in his fields planting $130 worth of seeds on his farm. He expects that the seeds he planted will yield $300 worth of wheat. What is the total opportunity cost Farmer Tony incurred for his spring day in the field planting wheat?