Answer:
I think the answer is A=49
 
        
             
        
        
        
Hi! Your answer is below!
Answer- Here's a simple model:
<span><span>X⟶f⟶Y
This is just something to help you out! I found it while searching on the internet! I have no Idea what the answer is, but in my defense, I think it's going to be choice 3!
Srry if I couldn't help! Glad if I could help!</span></span>
        
             
        
        
        
1 = 90
2 = 65
3 = 65
4 = 25
90+25=115
180-115=65
have a merry christmas :)
        
             
        
        
        
Answer:
i)W = 2500 / T
ii)  W = 500 Tons
iii) grad W(10°) = - 25î
iv) The formulation is not practical
Step-by-step explanation:
i)  Write an equation describing the use of coal
As use of coal is inversely proportional to the average monthly temperature
if  W is use of coal in tons/per month then
W(t)  =   k / T              where k is a constant of proportionality and T is the average temperature in degrees. We have to determine k from given conditions
k  =  ??   we know that when   T  =  25°    W = 100 tons  the by subtitution
W = k/T           100  =  k /25       k  =  2500 Tons*degree
Then final equation is:
W = 2500 / T
ii) Find the amount of coal when T = 5 degrees
W = 2500 / 5
W = 500 Tons
iii)
The inverse proportionality implies that W will decrease as T increase.
The vector gradient of W function is:
grad W  = DW(t)/dt î   
grad W  = - 2500/T² î
Wich agrees with the fact that W is decreasing.
And when T = 100°
grad W(10°) =  - 2500/ 100 î      ⇒  grad W(10°) = - 25î
iv) When T =  0  The quantity of coal tends to infinite and the previous formulation is not practical