Este: $RCOOR'$
Muối: $RCOONa$
Bảo toàn nhóm COO:
$\dfrac{17,6}{R+R'+44}=\dfrac{19,2}{R+44+23}$
$\Leftrightarrow 19,2R+19,2R'+844,8=17,6R+1179,2$
$\Leftrightarrow 1,6R+19,2R'=334,4$
$\Leftrightarrow R+12R'=209$
$\Rightarrow R=29; R'=15$
Vậy este là $CH_3-CH_2-COOCH_3$
=> chọn B