Mathematics - Permutation & Combination Question with Solution | TestHub

Let $\mathrm{A}=\left\{{\mathrm{x}}_1,{\mathrm{x}}_2,{\mathrm{x}}_3\dots .{\mathrm{x}}_7\right\},\mathrm{B}=\left\{{\mathrm{y}}_1{\mathrm{y}}_2{\mathrm{y}}_3\right\}$. The total number of functions f : $\mathrm{A}\to \mathrm{B}$ that are onto and there are exactly three elements $x$ in $A$ such that $f(x)=y_2$, is equal to