Recursive equation would be f(x+1) = f(x) - 25 with f(0) = 300
Explicit equation would be f(x) = -25x + 300
And graph would looks like this: 
 
        
        
        
Answer:
80,000
Step-by-step explanation:
I hope this helps:)
 
        
             
        
        
        
About 3.8 hours, if asking for a whole number round to 4