If $\mathrm{a}, \mathrm{b}, \mathrm{x}, \mathrm{y}$ are positive numbers such that $\mathrm{a}+\mathrm{b}+\mathrm{x}+\mathrm{y}=5$, then the maximum possible value of $(\mathrm{a}+\mathrm{b})(\mathrm{x}+\mathrm{y})$ is
(a) $\frac{5}{2}$
(b) 5
(c) $\frac{25}{4}$
(d) $\frac{25}{2}$