Joyce has decided to volunteer to work in the local High Street Charity Shop. She has agreed to be in the shop for 4 hours on a Saturday. To get from her home to the High Street, Joyce will have to travel by bus. Her walk from home to the bus stop is no more than 5 minutes, and the bus journey each way takes between 20 and 30 minutes depending on traffic. Buses from Joyce's home leave for the High Street at 30 minute intervals, on the hour and on the half hour. Return buses for Joyce leave the High Street at 30 minute intervals, at 15 minutes past the hour and 15 minutes to the hour. The walk to and from the bus stops to the Charity Shop is no more than 5 minutes. Joyce wants to catch the 13:45 bus home after working in the shop.