Answer:
So % increment in tool life is equal to 4640 %.
Explanation:
Initially n=0.12 ,V=130 m/min
Finally C increased by 10% , V=90 m/min
Let's take the tool life initial condition is
and when C is increased it become
.
As we know that tool life equation for tool

At initial condition
------(1)
At final condition
-----(2)
From above equation


So increment in tool life =

=

So % increment in tool life is equal to 4640 %.