An experiment found that primary production in a plant community was higher if giant bunchgrass was included in the mixture, just because giant bunchgrass grows really large. This is an example of a diversity effect caused by which mechanism?

In a high school with 3000 students, counselors are putting together a math tutoring program for the neighboring middle school. they plan to invite high school students with high average test scores to tutor middle school students, and they would like to offer gift cards to the student tutors. the counselors have a spreadsheet showing each student’s average test scores, and in order to find out how many gift cards they should purchase, the counselors need to count how many students would qualify to become tutors. which type of function would best the counselors determine the number of eligible students?