an administrative assistant at a software company often provides breakfast when there is a morning meeting. for last weeks sales, she purchased 3 dozen doughnuts and 5 dozen croissants, spending a total of $60. in preparation for yesterday's safety meeting, she spent $65 on 4 dozen doughnuts and 5 dozen croissants. assuming she purchased the items at the same bakery both times, how much does a dozen of each cost?