Q-28.

Under the initial set of assumptions, $u = e^{\sigma\sqrt{\Delta t}} = e^{0.2840\sqrt{1}} = 1.32950$ and $d = 1 / 1.32950 = 0.75216$, such that $p = d = 0.50$.

If the dividend is included, then $p = \frac{e^{(r-q)\Delta t} - d}{u - d} = 0.46427$. Therefore, $d = 1 - 0.46427 = 0.53573$, and the increase is about 3.570%.