The administrative assistant at a software company often provides breakfast when there is a morning meeting. For last week's sales meeting, she purchased 2 dozen doughnuts and 8 dozen croissants, spending a total of $72. In preparation for yesterday's safety meeting, she spent $92 on 7 dozen doughnuts and 8 dozen croissants. Assuming she purchased the items at the same bakery both times, how much does a dozen of each cost?