At what mL/HR would you set your pump?

The correct answer is option 300mL/hr.
Since you need to give 4gm of magnesium sulfate over 20 minutes and it comes in 40gm/1000mL
You do the following:
Divide 4gm by 40gm and multiply by 1000mL
4/40 = 0.01

0.01* 1000 = 100
Divide one hour (60 minutes) by 20 and multiple the results by 100
60/20
3 * 100 = 300
Therefore, you will set the pump at 300mL/hour to administer 4gm Magnesium sulfate IV in 20 minutes.
Hope this helps.