$3.$ The overall mass transfer coefficient $($K$)$ is influenced by the $\_\_\_$ of the individual phase mass transfer coefficients, the $\_$ area, and the $\_\_\_$ resistance.

$-$ a$)$ sum, interfacial, diffusion

$-$ b$)$ product, surface, thermal

$-$ c$)$ reciprocal, phase boundary, overall

$-$ d$)$ difference, phase volume, chemical