Given a list of grades, calculate the median of the list.
90, 70, 80, 75, 85
The sorted grades are 70, 75, 80, 85, 90. Therefore, the median grade is 80.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Given a list of grades, calculate the median of the list.

### Response:
The sorted grades are 70, 75, 80, 85, 90. Therefore, the median grade is 80.