  We present here the results of broadband spectral analysis of low-mass X-ray
binary and a black hole candidate 4U 1957+11. The source was observed nine
times with the Nuclear Spectroscopic Telescope Array (NuSTAR) between 2018
September and 2019 November. During these observations, the spectral state of
4U 1957+11 evolved marginally. The disc dominant spectra are well described
with a hot, multicolour disc blackbody with disc temperature varying in the
range $kT_{\rm in} \sim$ 1.35-1.86 keV and a non-thermal component having a
steep slope ($\Gamma =$ 2-3). A broad Fe emission line feature (5-8 keV) was
observed in the spectra of all the observations. The relativistic disc model
was used to study the effect of distance, inclination, and the black hole mass
on its spin. Simulations indicate a higher spin for smaller distances and lower
black hole mass. At smaller distances and higher mass, spin is maximum and
almost independent of the distance. An inverse correlation exists between the
spin and the spectral hardening factor for all the cases. The system prefers a
moderate spin of about 0.85 for black hole masses between 4-6 M_sun for a 7 kpc
distance.
