Suppose there are three successive operations for a production process. Each operation is operated by a unique work center. Each work center can only process one unit simultaneously. The run time per unit for each operation $($in minutes$)$ is:$$

Operation

$1$

$2$

$3$

Time

$10$

$6$

$8$

$$

If the manager wants to increase the process capacity through process improvement,$$which operation should be focused on at first?$$

All of the three operations equally

Operation $2$

Operation $1$

Operation $3$