Few points to keep in mind.
- When process is scheduled first Step 3 not required.
- When process is scheduled for last time step 1 not required.
Ref: https://cs.stackexchange.com/questions/74049/does-a-context-switch-happen-when-a-process-has-terminated
Total time used for process = 2 * k * 10 (Each process is gets 2 time slice of 10 ms.)
In 1st cycle it takes $kT_{1}$ for selecting which process to schedule and $T_{0}$ for saving the context.
In 2nd cycle it takes $kT_{1}$ for selecting which process to schedule and $T_{0}$ for restoring the context.
Total Time = $2 * k * 10 + 2k (kT_{1} + T_{0} )$
$CPU$ $Utitlization =$ $\frac{ Useful Work}{Total Time}$
= $\frac{ 2 * k * 10}{2 k(kT_{1} + T_{0} ) + 2 * k * 10 }$
= $\frac{ 10k}{ k^2T_{1} + kT_{0} + 10k }$