  The exact origins of many Type Ia supernovae$\unicode{x2013}$progenitor
scenarios and explosive mechanisms$\unicode{x2013}$remain uncertain. In this
work, we analyze the global Suzaku X-Ray spectrum of Kepler's supernova remnant
in order to constrain mass ratios of various ejecta species synthesized during
explosion. Critically, we account for the Suzaku telescope effective area
calibration uncertainties of 5$\unicode{x2013}$20% by generating 100 mock
effective area curves and using Markov Chain Monte Carlo based spectral fitting
to produce 100 sets of best-fit parameter values. Additionally, we characterize
the uncertainties from assumptions made about the emitting volumes of each
model plasma component: finding that these uncertainties can be the dominant
source of error. We then compare our calculated mass ratios to previous
observational studies of Kepler's SNR and to the predictions of SN Ia
simulations. Our mass ratio estimates require a $\sim$90% attenuated
$^{12}$C$+^{16}$O reaction rate and are potentially consistent with both near-
and sub-M$_{\rm Ch}$ progenitors, but are inconsistent with the dynamically
stable double detonation origin scenario and only marginally consistent with
the dynamically unstable dynamically-driven double-degenerate double detonation
(D$^6$) scenario.
