RATE AT vs RATE OF

“The Rate of” Vs “The Rate at”

Consider the following example:

The rate at which people drive cars.(Correct)
The rate of cars driven by people. -- This option changes the meaning and is wrong here.

Whenever we refer to the speed/velocity we use it as THE RATE AT.

Whenever we refer to the prices we use it as THE RATE FOR.

For e.g.

State officials report that soaring rates of liability insurance have risen to force cutbacks in the operations of everything from local governments and school districts to day-care centers and recreational facilities.

(A) rates of liability insurance have risen to force

(B) rates of liability insurance are a force for

(C) rates for liability insurance are forcing

(D) rises in liability insurance rates are forcing

(E) liability insurance rates have risen to force

The correct answer is C as it refers to the price of liability insurance.