According to the circular-flow diagram GDP
a)can be computed as either the revenue firms receive from the sales of goods and services or the payments they make to factors of production.
b)can be computed as the revenue firms receive from the sales of goods and services but not as the payments they make to factors of production.
c)can be computed as payments firms make to factors of production but not as revenues they receive from the sales of goods and services.
d)cannot be computed as either the revenue firms receive or the payments they make to factors of production.