Answer
(a) Potential Energy, $U$ actually increases as $r$ increases.
(b) Speed is less than at $f$ when the electron is at $i$.
Work Step by Step
The electric potential energy due to a charge placed a distance $r$ form the center of the positive point charge is
$U=\frac{1}{4\pi \epsilon_{0}}$$\frac{q_{1}q_{2}}{r}$
The potential energy varies as $\frac{1}{r}$ but because the two charges have opposite signs, hence increasing $r$ simply means $U$ decreases but $U$ actually increases.
(b) Since, two opposite charges slow down as they move farther apart, hence the speed decreases due to deceleration.
Speed is less than at $f$ when the electron is at $i$.
