Amanda left Bob's house and drove toward the ocean. Two hours later, Bob left, driving 20 mph faster than Amanda in an effort to catch up with her....

Amanda left Bob's house and drove toward the ocean. Two hours later, Bob left, driving 20 mph faster than Amanda in an effort to catch up with her. After four hours, Bob caught up with Amanda. What was each person's average rate?

Please include the following in your work

a) a statement defining any unknown quantities in the problem in terms of variables.

b) an equation involving the variable(s) corrersponding to the information given in the problem