The Thevenin equivalent between a and b for the given circuit given below is

$V_{th}=20V,R_{th}=7\mathrm{.}2$

$V_{th}=24V,R_{th}=4\mathrm{.}8$

$V_{th}=16V,R_{th}=5\mathrm{.}6$

$V_{th}=14V,R_{th}=3\mathrm{.}6$