9 friends are living in 9 different flats of an apartment. Each of them was allotted a parking spot to park their cars in the ground floor. But they used to park their cars randomly in any of the 9 parking spots. In how many ways can they park their cars so that exactly 7 people park their cars in the spots allotted to them?  Choices.
A) 24
B) 36
C) 48
D) 60
E) 72
9C7 = 36   The remaining 2 people in each case will be parked in each other's parking spots.   The answer is 36.
<result>B</result>
9 friends are living in 9 different flats of an apartment. Each of them was allotted a parking spot to park their cars in the ground floor. But they used to park their cars randomly in any of the 9 parking spots. In how many ways can they park their cars so that exactly 7 people park their cars in the spots allotted to them?