Three friends, Nakobe, Mikah, and Ashton, are saving up money to buy microphones for their podcast. The total cost of the microphones is represented by the expression 7x2 − 2x + 11.

The friends have already saved the following amounts:

Nakobe: x2
Mikah: x − 15
Ashton: 5x + 2

Which expression represents the amount of money the friends still need to buy the microphones?

6x2 − 8x + 24
6x2 − 8x − 2
x2 + 6x − 17
x2 + 6x − 13