Answer
We can rank the situations according to the charge on the inner surface of the shell:
$(2) \gt (1) \gt (3)$
Work Step by Step
The net electric field within the metal must be zero. Therefore, the enclosed charge within the shell (including the inner surface) must be zero. That is, the sum of the charge on the inner surface and the charge on the ball must be zero.
We can find the charge $Q$ on the inner surface of each shell:
(1) $+4q+Q = 0$
$Q = -4q$
(2) $-6q+Q = 0$
$Q = +6q$
(3) $+16q+Q = 0$
$Q = -16q$
We can rank the situations according to the charge on the inner surface of the shell:
$(2) \gt (1) \gt (3)$
