what volume of ammonia, in dm3 can be made from 30 dm3 of nitrogen and 60dm3 of hydrogen?

all volumes are at same pressure and temp.

reaction goes to completion according to the equation:

N2 + 3h2 --> 2nh3

N2 + 3H2 --> 2NH3

This question is based on the concept :At same temperature and pressure, gases react or formed  in a simple ratio by volume in a Chemical reaction.
Here 30 dm3 N2 will give 2*30 dm3 of NH3 = 60 dm3
and 60 dm3 of H2 will give 2/3 *60 NH3=40 dm3
H2 is the limiting reactant and hence it is 40 dm3