Answer
$a=2, b=1, c=3$
Work Step by Step
The formula defining capacitance using area and separation is the formula $$C=\frac{\epsilon_o A}{d}$$ Plugging in values for each yield $$C_1= \frac{\epsilon_o A}{d}$$ $$C_2=\frac{\epsilon_o (2A)}{d}=\frac{2\epsilon_o A}{d}$$ $$C_3=\frac{\epsilon_o A}{2d}$$ Ordering these capacitances from least to greatest gives $C_3,C_1,C_2$. Since $q=CV$, as capacitance increases, charge increases. Therefore, the capacitor with the lowest capacitance has the flattest slope and the capacitor with the highest capacitance has the steepest slope. Therefore, $a=2, b=1, c=3$.
