  In power-law cosmology, we determine potential function of a canonical scalar
field in FLRW universe in presence of barotropic perfect fluid. The combined
WMAP5+BAO+SN dataset and WMAP5 dataset are used here to determine the value of
the potential. The datasets suggest slightly closed universe. If the universe
is closed, the exponents of the power-law cosmology are $q = 1.01$ (WMAP5
dataset) and $q=0.985$ (combined dataset). The lower limits of $a_0$ (closed
geometry) are $5.1\E{26}$ for WMAP5 dataset and $9.85\E{26}$ for the combined
dataset. The domination of the power-law term over the curvature and barotropic
density terms is characterised by the inflection of the potential curve. This
happens when the universe is 5.3 Gyr old for both datasets.
