Answer:
I believe it's C, but I could be wrong
Step-by-step explanation:
You are right. 5 is correct.
profit=f(x)
so solve for f(x)=1000
1000=70n-400
add 400 to both sides
1400=70n
divide both sides by 70
20=n
20 students need to be enrolled to make a profit of 1000.00