Let's turn that into a linear system:

Set the equations equal to each other and solve:



We then plug in to get

:

The solution to the system is

.
Now, let's turn our attention to the statements.
The first one is
false: Emilia's rate is higher, and the two plans cost the same at 50 texts, after which point Hiroto's plan becomes
cheaper!
The second one is also
false: we already figured out that the lines intersect at

.
The third statement is also
false: as above, the lines intersect at

.
The fourth statement is
true: the lines intersect at

.
In conclusion, the fourth statement - "Both plans cost the same when 50 texts are sent" - is true.