Can you explain just part C please.

1-Consider three different processors P1, P2, and P3 executing the same instruction set. P1 has a 3 GHz clock rate and a CPI of 1.5. P2 has a 3 GHz clock rate and a CPI of 1.0. P3 has a 2.5 GHz clock rate and has a CPI of 2.2.

a. Which processor has the lowest performance expressed in instructions per

second?

Performance of P1 (Instructions/sec) = 3 X 10⁹ / 1.5 = 2 X 10⁹

Performance of P2 (Instructions/sec) = 3 X 10⁹/ 1.0 = 3 X 10⁹

Performance of P3 (instructions/sec) = 2.5 X 10⁹/ 2.2 = 1.13 X 10⁹

b. If each processor executes a program in 25 seconds, find the number of cycles and the number of instructions.

Cycles(P1) = 25 X 3 X 10⁹ = 75 X 10⁹ s

Cycles(P2) = 25 X 3 X 10⁹ = 75 X 10⁹ s

Cycles(P3) = 25 X 2.5 X 10⁹ = 62.5 X 10⁹ s

c. We are trying to reduce the execution time by 10% but this leads to an increase of 5% in the CPI. What clock rate should we have to get this time reduction?