Are these sentences correct:
1-If they are only a mile away, they must get here in time.
2-If they have advanced technology, then they must solve this problem. (meaning: it is almost certain that they will solve it... they must be able to solve it)
3-If they have fifty men working for them, they must build that house in less than two weeks. (meaning: it is almost certain that they will build that house in two weeks...)
I think "should" would probably be better here, but I don't see why "must" should be incorrect, especially if one wants to express very high liklihood.