Mass Spectrometry question help

Hi,

I'm studying AS OCR chemistry and I'm not sure how to answer one of the questions on Mass Spectrometry.

Question: A sample of Hydrogen containing the Isotopes Hydrogen-1, Hydrogen-2 and Hydrogen-3 was analysed in a Mass Spectrometer. How many peaks corresponding to H2+ would be expected?

The answer is 5 but I have no idea how/why that is the answer.

Any help would be appreciated

In a molecule there are two atoms and either of the atoms can be 1H, 2H or 3H

How many possible combinations are there?

I thought of that, but wouldn't that only provide three combinations?

1H + 2H
1H + 3H
2H + 3H

Unless I'm missing something (which is highly likely!)

What about 1H + 1H, 2H + 2H and 3H + 3H?

What would the m/z values of the six peaks be?