$6.$ The concept of an ideal stage assumes $\_\_\_$ mixing within the stage, instantaneous $\_,$ and the outgoing streams are in $\_\_\_$ with each other.

$-$ a$)$ partial, mass transfer, disequilibrium

$-$ b$)$ complete, equilibrium, equilibrium

$-$ c$)$ minimal, heat transfer, phase contact

$-$ d$)$ no$,$ diffusion, steady state