Economical means "thrifty, efficient".
Economic refers to "monetary aspects."
I have explained the difference using 3 examples.EG:
(SOURCE: OG)
Although shistosomiasis is not often fatal,
it is often so debilitating that is has become an economic drain on many developing countries.
A.it is often so debilitating that is has become an economic
B.it is of such debilitation, it has become an economical
C.so debilitating is it as to become an economic
D.such is its debilitation, it becomes an economical
E.there is so much debilitation that it has become an economical
Since in the question it refers to MONETARY DRAIN the the word used should be ECONOMIC. That leaves us with A and C. C has incorrect idiom used..
The supply of oil being finite has become an economical and political consideration of the first magnitude for all modern industrial nations.
(A) The supply of oil being finite has become an economical
(B) The finite supply of oil has become an economical
(C) That the supply of oil is finite has become an economical
(D) The supply of oil being finite has become an economic
(E) That the supply of oil is finite has become an economic
Since it again refers to monetary considerations, the word used will be economic.
This leaves us with D and E.
To develop more accurate population forecasts, demographers
have to know a great deal more than now about the social and economic determinants of fertility.
A. have to know a great deal more than now about the social and economic
B. have to know a great deal more than they do now about the social and economical
C. would have to know a great deal more than they do now about the social and
economical
D. would have to know a great deal more than they do now about the social and
economic
E. would have to know a great deal more than now about the social and economical
Here, we are referring to the efficient determinants, hence ECONOMICAL is used. This leaves us with B, C , E.
Please feel free to ask questions if anything is not not clear..
If my post is helpful, give kudos... 
33% (00:00) correct
2
