Let $a, b, c$ and $d$ be real numbers such that
$$x + ay \leq b$$
$$x + cy \geq d$$
The solution set of the system of inequalities is shown in green on the coordinate plane below.
Accordingly, what are the signs of the numbers $a, b, c$ and $d$ in order?
A) $+, -, -, -$
B) $+, +, +, -$
C) $+, -, +, -$