The rate at which the risk of Down syndrome is changing is approximated by the function
r(x) = 0.004641x2 − 0.3012x + 4.9 20 ≤ x ≤ 45
where r(x) is measured in percent of all births per year and x is the maternal age at delivery.
Find a function f giving the risk as a percentage of all births when the maternal age at delivery is x years, given that the risk of Down syndrome at age 20 is 0.23% of all births.

Question

The rate at which the risk of Down syndrome is changing is approximated by the function
r(x) = 0.004641x2 − 0.3012x + 4.9    20 ≤ x ≤ 45
where r(x) is measured in percent of all births per year and x is the maternal age at delivery. 
Find a function f giving the risk as a percentage of all births when the maternal age at delivery is x years, given that the risk of Down syndrome at age 20 is 0.23% of all births.