Resource overutilization

After reading the documentation, and searching the web site it seems that MrProject does not consider resource utilization.  Consider this scenario:

Project start date 1/1/2003 containing only two tasks: Task1 and Task 2.

Task1 duration 10 days starting 1/1/2003
Task2 duration 20 days starting 1/1/2003

Person A for 100% on Task 1
Person A for 100% on Task 2

MrProject reports that the total time for Task1 and Task 2 is the maximum of the two tasks (20 days), instead of 30 days.  This assumes that Task1 and Task2 can be done simultaneously.  

How can I get MrProject to either: tell me when a resource is overutilized, or move the start and end dates of a task to prevent the overutilization?

Thanks in advance,
Ben Pracht