Should I use 'for'?

[Ulysses]

I'm wondering if I need to use the preposition 'for' between 'pay' and 'the medical bill' in the sentence:

Patients become unnecessarily stressed when they have to think about how they are going to pay the medical bill.

The sentence sounds awkward and I'm not sure if inserting 'for' will correct it like:

Patients become unnecessarily stressed when they have to think about how they are going to pay for the medical bill.

[rws_killer5]

Both are correct.