What if the 'or' is exclusive instead of inclusive? The context is an integer programming problem on choosing projects to maximise profit.
I think (b) i. changes if 'either project 1 or project 3' means 'project 1 xor project 3' rather than 'project 1 or project 3'



What I tried:
Let $x_i =$
$1$, if project i is selected and $0$, otherwise.
and
$c_{ij}$ be the expenditure in project i in year j
Obj func: Max
$$z = r \cdot x - \sum_{i} x_ic_{i1} - \sum_{i} x_ic_{i2} - \sum_{i} x_ic_{i3}$$
where
$r_i$ is the return of project i
$$r' = [10, 40, 20, 15, 30]$$
$$x' = [x_1, x_2, x_3,x_4, x_5]$$
s.t.
$$\sum_{i} x_{i}c_{i1} \le 25$$
$$\sum_{i} x_{i}c_{i2} \le 25$$
$$\sum_{i} x_{i}c_{i3} \le 25$$

bii
$$x_2 + x_4 \le 1$$

bi
if either-or means or (inclusive or):
$$x_4 \ge x_1, x_4 \ge x_3$$
if either-or means xor (exclusive or):
$$x_4 \ge x_1 + x_3 - y$$
where $y=2$ if $x_1 = x_3 = 1$ and $0$ otherwise.

Is that right?

From Chapter 3 here.

As mentioned in the comments English is ambiguous. However, the standard has evolved that "or" always means inclusive or. It never means exclusive or.
Again, this is a convention of English language that's widely but not universally used, but is always my first assumption.
