SQL - Updating the hours from the Previous Records

We have a table which has the task records of all employees. The required spent hours is 9.5 (excluding lunchbreak) per day, whatever exceeds on that will be in the unpaidspent column.

Before, we used to leave the lunch as blank but now as they required to have the lunch as a task, the hour/minutes located on that lunchbreak is being included in the 9.5 required spenthours. Now

1. How to move the breaktime value from spent to unpaid?

2. After the update, How can we deduct the breaktime unpaid to the last task unpaid and move it to the spenthours to complete the required 9.5 spent hours per day?

 

Thank you.