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 wanted 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 variable of interest to the researcher.
A.
the textbook cost of first-year Drummand University students
B.
the year in school of Drummand University students
C.
the age of Drummand University students
D.
the cost of incidental expenses of Drummand University students