Write test cases for shopping scenario

There are 3 girls in shopping mall, where they have the offer ""Rs 10 off on purchase of Rs 50 or above""..Now they all bought some good{girl 1- Rs 67, girl 2- 43, girl 3 - 17}. now what they do is they combine there good (girl 3 and girl 2) and they together pay rs- (57+50= 117), so as girl 3 and girl 2 satisfies the criteria and get Rs 10 off. the amount can be used is between 1-99. write the test cases on the above statement.

Rs 57 - because the cost of girl 1 is 67 hence 10 rs off
Rs 50- because the cost of good girl bought (43+17=60) hence 10 off i.e. 50