  We investigate the evolution of differential emission measure distribution
(DEM[T]) in various phases of a B8.3 flare, which occurred on July 04, 2009. We
analyze the soft X-ray (SXR) emission in 1.6-8.0 keV range, recorded
collectively by Solar Photometer in X-rays (SphinX; Polish) and Solar X-ray
Spectrometer (SOXS; Indian) instruments. We make a comparative investigation of
the best-fit DEM[T] distributions derived by employing various inversion
schemes viz. single gaussian, power-law, functions and Withbroe-Sylwester (W-S)
maximum likelihood algorithm. In addition, SXR spectrum in three different
energy bands viz. 1.6-5.0 keV (low), 5.0-8.0 keV (high) and 1.6-8.0 keV
(combined) is analyzed to determine the dependence of the best-fit DEM[T]
distribution on the selection of energy interval. The evolution of DEM[T]
distribution, derived using W-S algorithm, reveals the plasma of multi-thermal
nature during the rise to the maximum phase of the flare, while of isothermal
nature in the post-maximum phase of the flare. Thermal energy content is
estimated considering the flare plasma to be of 1) iso-thermal and 2)
multi-thermal nature. We find that the energy content during the flare,
estimated from the multi-thermal approach, is in good agreement with that
derived using the iso-thermal assumption except during the maximum of the
flare. Further, (multi-) thermal energy estimated employing low-energy band of
the SXR spectrum result in higher values than that derived from the
combined-energy band. On the contrary, the analysis of high-energy band of SXR
spectrum lead to lower thermal energy than that estimated from the
combined-energy band.
