Bob is a retired teacher living in New York City who teaches clarinet lessons to supplement their normal income. At an hourly wage rate of $15, they are willing to teach 3 hours per week. Upping the wage to $30 per hour, they are willing to teach 8 hours per week. Using the midpoint method, the elasticity of Bob's labor supply between the wages of $15 and $30 per hour is approximately , which means that Bob's supply of labor over this wage range is