Suppose that D\displaystyle {D} and R\displaystyle {R} are sets, given as shown below. How many functions are possible from D\displaystyle {D} to R\displaystyle {R} or a subset of R\displaystyle {R}?

D={1,3,7,8,9}\displaystyle {D}={\left\lbrace{1},{3},{7},{8},{9}\right\rbrace}     R={t,x}\displaystyle {R}={\left\lbrace{t},{x}\right\rbrace}

Answer: different functions