John has three options for summer work. He can do lawn work for $100 per week, babysit for $125 per week, or work at the local pool for $175 per week. All of the options would require approximately 20 hours of work per week. In addition, if he chooses to work at the pool, he will incur $20 in gas costs per week. What is the opportunity cost if he chooses to babysit?