If f(x) = x^3 - 2x^2 , which expression is equivalent to ff(i)?

Twenty-five percent of the customers entering a grocery store between 5 p.m. and 7 p.m. use an express checkout. consider five randomly selected customers, and let x denote the number among the five who use the express checkout.

896.31 cm= km 100cm = 1m 1000m = 1km a) 0.0089631 b) 0.0089631 c) 8.9631 d) 89.631

Math it's appreciated. (picture provided)