In the bus scheduling example $($Example $2\mathrm{.}4-5),$ suppose that the number of buses needed during different time slots has changed to the following:

$12-4$ am

$6$

$4-8$ am

$10$

$8$ am$-12$ pm

$12$

$12-4$ pm

$9$

$4-8$ pm

$15$

$8$ pm$-12$ am

$7$

The city has $3$ alternatives,

Use six $8-$hours shifts only $($just like the example$),$ each driver is paid $$80$ per shift.

Use six $12-$hours shifts only, each driver is paid $$140$ per shift $($including the extra hours at $150\%$ of the regular hourly pay$).$

Use a combination of $8-$ and $12-$hour shifts. Each driver is paid $$80$ per $8-$hour shift, or $$140$ per $12-$hour shift.

How much salaries will be paid $($in minimum$)$ for alternative #$3$ per day?$$