Consider the boundary-value problem $y^{\prime \prime}-2 y^{\prime}+2 y=0$, $y(a)=c, y(b)=d$.
(a) If this problem has a unique solution, how are $a$ and $b$ related?
(b) If this problem has no solution, how are $a, b, c$, and $d$ related?
(c) If this problem has infinitely many solutions, how are $a, b, c$, and $d$ related?