Two friends, haley and kristen, are growing out their hair. they plan to cut it off at a certain point and donate it to a charity that makes wigs for people with cancer. haley's hair is already 19 centimeters long and grows at a constant rate of 1 centimeter per month. kristen's hair is 11 centimeters and growing at a speed of 3 centimeters per month. if the girls get their hair cut on a certain day, they will have exactly the same length to donate. how long will their hair be? how long will that take?