If the parabola y=ax2+bx+c has vertex at (4, 2) and a∈[1,3], then the absolute difference between the extreme values of abc is
(3)
-b2a=4⇒b=-8a
16a+4b+c=2
c=16a+2
As a∈[1,3]⇒c∈[18,50]