Most analysts focus on the cost of tuition as the way to measure the cost of a college education. But​ incidentals, such as textbook​ costs, are rarely considered. A researcher at Drummand University wishes to estimate the textbook costs of​ first-year students at Drummand. To do​ so, she monitored the textbook cost of 250​ first-year students and found that their average textbook cost was​ $600 per semester. Identify the population of interest to the researcher.