Hester is going for a job interview. She needs to travel by railway between Birmingham and Derby, but she needs to stop off in Tamworth for an hour on the way out to see her former teacher for some coaching. When at Derby, she needs an hour and a half to go to the prospective employer to take an aptitude test. She can fix her appointments for any time in the day. Naturally, she wants to make the journey in the most efficient way so that it takes the least possible time. This is the railway timetable: