Given that 0.403 g of nitrogen combines with 0.0864 g of hydrogen and h is assigned an atomic mass of 1.00 amu calculate the atomic mass of nitrogen based on the formula nh.

If the molecular formula is NH, then it means there are 1 molecule of nitrogen every 1 molecule of hydrogen. In this case, the hydrogen atomic mass is 1 and its weight is 0.0864 grams. The nitrogen weight 0.403 grams and we need to find the atomic mass. The calculation should be:

(1/ 0.0864 gram) * 0.403 = 4.66

I'm not sure that there is NH molecule. The molecular weight of nitrogen should be 14 so the question might be wrong. If the reaction is N2 + 3 H2 → 2 NH3 
Then the answer is: (3/ 0.0864 gram) * 0.403 = 14

The most plausible answer is b, duration. the given amount of time is considered how long it last for.