Answer
(a) Electrons were added to the balloon.
(b) $3.75\times 10^{9}$ electrons were transferred to the balloon.
Work Step by Step
(a) Since the balloon acquired a negative charge, electrons were added to the balloon.
(b) We can find the number of electrons that were transferred:
$\frac{-0.60\times 10^{-9}~C}{-1.6\times 10^{-19}~C} = 3.75\times 10^{9}$
$3.75\times 10^{9}$ electrons were transferred to the balloon.
