Graphs of the Other Trigonometric Functions · Superchallenge problem

Build the function $y = a\csc(bx - c) + d$ with $a > 0$, $b > 0$ and $0 \le c < 2\pi$ that has period $2\pi$, adjacent vertical asymptotes at $x = \dfrac{\pi}{2}$ and $x = \dfrac{3\pi}{2}$, whose upward U-shapes have minimum value $2$ and whose downward U-shapes have maximum value $-6$, and whose branch between those two asymptotes is an upward U. Find $a$, $b$, $c$ and $d$.