Oi
Just calculating the differential. Step by step:

If you want to know where the tangent has no slope:
If Carla would have bought 4 plants it would have been 13 dollars from green touch
If she would have bought them for the grocery store it would have been 14 dollars
So in conclusion she saved 1 dollar
Option 3
full timers work 5 hours a day whereas Part timers work 3 hours a day!
<u>Step-by-step explanation:</u>
Here we have , The difference in hours between full times and the part timers to work three hours a day is 2 working hours . We need to find that how many hours per day to full timers work . Let's find out:
Let full timers work x hours , Part time workers work 3 hours a day , According to question, difference in hours between full times and the part timers to work three hours a day is 2 working hours i.e.
⇒ 
Adding 3 to make x term alone :
⇒ 
⇒ 
Therefore, full timers work 5 hours a day whereas Part timers work 3 hours a day!
-11-(-7)
-11+7
Your answer is -4
Is there like any image to see how big are the posts?