Answer:
5hours
Explanation:
1 week =7 days 
10 hr +20hr = 30 hrs 
If you work 4hrs a wee k you will achieve only 28hrs of work so you will have to work for 5hrs to achieve 35hrs of work which is still within the bracket of 40hrs of work 
In each job you will work for 2hours 30 
minute 
Each day you will earn $60.00
At tutoring you get $37.50
At sippy drink you will get $22.50
In a week you will get a maximum of $420.00