How to calculate clock frequency?

Question

Informatics

Let's assume that three different processors, P1, P2, and P3, execute the same set of instructions, while having the clock speeds and CPI values ​​shown in the table:

Processor CPI clock speed
1 2 GHz 1.5
2 1.5 GHz 1.0
3 3 GHz 2.5


V(P1)=2*10^9/1.5=1.3*10^9 instr/s
V(P2)=1.5*10^9/1=1, 5*10^9 instr/s
V(P3)=3*10^9/2.5=1.2*10^9 instr/s Trying

to cut time by 30%(10 sec) increases CPI by 20 %. Determine the clock frequency to obtain such a reduction in time.