Answer
The number of ways a customer can order a drink out of two drinks available in four sizes and five flavors = $2_{{C}{_{1}}}$ . $4_{{C}{_{1}}}$.$5_{{C}{_{1}}}$ = 40
Work Step by Step
The number of ways a customer can order a drink out of two drinks available in four sizes and five flavors = $2_{{C}{_{1}}}$ . $4_{{C}{_{1}}}$.$5_{{C}{_{1}}}$ = $\frac{2!}{(2 - 1)! 1!}\times\frac{4!}{(4 - 1)! 1!}\times\frac{5!}{(5 - 1)! 1!}$
= $\frac{2!}{1! 1!}\times\frac{4!}{3! 1!}\times\frac{5!}{4! 1!}$
= $\frac{2\times1!}{2! .1!}\times\frac{4\times3!}{3! .1!}\times\frac{5\times4!}{4! .1!}$
= $2\times4\times5$ = 40
