Let A ={x_1, x_2, …, x_7} and B ={y_1, y_2, y_3} be two sets containing seven and three distinct elements respectively. Then the total number of…

Let $\displaystyle \mathrm{A}=\left\{x_1, x_2, \ldots, x_7\right\}$ and $\displaystyle \mathrm{B}=\left\{y_1, y_2, y_3\right\}$ be two sets containing seven and three distinct elements respectively. Then the total number of functions $\displaystyle f: \mathrm{A} \rightarrow \mathrm{B}$ that are onto, if there exist exactly three elements $\displaystyle x$ in A such that $\displaystyle f(x)=y_2$, is equal to :