Hope says “joy and sadness mix together like cream in coffee.” what does she mean by that simile?

Cream and coffee mix easily. Joy and sadness mixes easily. The similie represents how emotions can change/mix considerably.

the cost of attendance or coa is an approximate budget for the cost of attendance of the whole academic year. in order to calculate this, universities take into consideration many factors like room and board, tuitions and fees, books, transportation and personal expenses such as medicine, laundry, clothing. all these factors combined make up the final sum to the cost of attendance in each university.