Let A and B be two finite sets having m and n elements respectively such that ` m lt n` . A mapping selected at random from the set of all mappings from A to B. The probability that the mapping selected is an injection is :

Options

A. `(n !)/((n-m)!m^(n))`
B. `(n!)/((n-m)!n^(m))`
C. `(m!)/((n-m)!n^(m))`
D. `(m!)/((n-m)!m^(n))`

Answer

B