Problem $5.$ A technician is charged with adjusting flow meters in gasoline pumps, which leads to penzene exposure. What would be the maximum air concentration of benzene that would maintain he incremental cancer risk below ${10}^{-6}?$ Assume the individual performs this job for $10$ years and an be either female or male. Exposure to gas fumes occurs for an average of $4$ hours per work day ith a work year consisting of $48$ five$-$day workweeks. Use values from Table $3-8$ in your calculations.