Questions

Central Processing Unit (CPU) is the brain of any computer system.

If as a business, you buy goods or services on credit from a supplier (accounts payable) then the supplier will supply the goods and business will incur a liability to the supplier for that amount, but no cash will change hands at that stage.

Some of those shop keepers allowed regular "trustworthy" customers to purchase items without having the full payment.

Hence, Buying on credit means that no actual money has changed hands.

CPU speed is the central factor in a computer's performance. And this CPU speed depends on the processor in the CPU chip. In a computer, clock speed refers to the number of pulses per second generated by an oscillator that sets the tempo for the processor. Clock speed is usually measured in Hertz (Hz).

But now-a-days, a pure processor's performance is measured in MIPS (Millions of Instructions Per Second). As here in the question, how a processor's speed is measured is asked and it is Hertz. 

Hence, Processor's speed of a computer is measured in Hertz(Hz) [MHz, GHz].