Note: Partially selective high school has majority of students from the mainstream, hence if they were to segregate their students in Yr11/Yr12, the selective stream of students (max 60) will have very VERY limited choices in subjects to choose from. Thus, the only way is to combine all students...
solving using simultaneous equations given discriminate = 0 gave the answer to 16ci) as above and it turns out that the y ordinate is y=-1/2+C.
Also since the parabola is y=x^2 i.e. concave up with vertex at (0,0) then it follows that the y-ordinate y=-1/2+C has to be >0 -------- i.e...