the administrative assistant at a software company often provides breakfast when there is a morning meeting. For last week's sales meeting, she purchased 9 dozen doughnuts and 9 dozen croissants, spending a total of $135. In preparation for yesterday's safety meeting, she spent $102 on 8 dozen doughnuts and 6 dozen croissants. Assuming she purchased the items at the same bakery both times, how much does a dozen of each cost?​