C(x) = 400 + 20x - 0.2x²
c(30) = 400 + 20(30) - 0.2(30)²
= 400 + 600 - 0.2(900)
= 1000 - 180
= 820
It costs $820 when 30 radios are produced.
Marginal cost is how much it would cost to make one MORE of the same product so now we find how much it costs to produce 31 radios and compare the two.
c(31) = 400 + 20(31) - 0.2(31)²
= 400 + 620 - 0.2(961)
= 1020 - 192.2
= 827.8 or ≈828.
Now we find the difference which means we subtract the two.
828 - 820 = 8.
Your marginal cost is $8.
To compare we can also do 29 radios.
c(29) = 400 + 20(29) - 0.2(29)² = 811.8 or ≈812
820 - 812 = 8.
Answer:
10 
Step-by-step explanation:
Hi there, hope you are having a nice day!
All we should do is plug in the value of b:
12-2
10 (Answer)
Hope you find it helpful.
Feel free to ask if you have any questions.

Answer:
9/10
Step-by-step explanation:
She lost 1/10 and 8/10 marbles. When you add them up you get 9/10. There for, Christina lost 9/10 marbles altogether.
Hope this helps :)
Answer:
4/3
Step-by-step explanation:
Given two points, we can find the slope by using
m = (y2-y1)/(x2-x1)
= (20 - -16)/(7 - -20)
= (20+16)/(7+20)
= 36/27
=4/3