For this sentence, it looks like the verb "to enter" is in the informal form (はいる as opposed to 入ります--the former being informal, the latter being formal). However, the verb "to need" / "costs" is in the formal -masu form (いります). As such, I was wondering why there are two different verb forms in one sentence. In other words, is this sentence (as a whole) formal or informal?
The following sentence would be grammatically incorrect, right?
It definitely looks incorrect, but I would appreciate someone clarifying why. :)