The answer would be the first choice.  
Explanation: The reason for this is that the question was pretty much just asking what the area of the resulting two-dimensional cross section would be -the shape in gray- (which can be found by using the formula  . To add on, since the dimensions of the shape are already given (5 and 3) all you've to do is multiply: 3*5=15
. To add on, since the dimensions of the shape are already given (5 and 3) all you've to do is multiply: 3*5=15 
That's how you get to the answer. 
 
        
                    
             
        
        
        
I think it’s X=1 for answer
        
             
        
        
        
I believe the answer is y = -5/2x + 6
        
             
        
        
        
Check the picture below.
so, a cone, that fits inside the cylinder, will have the same height "h" and radius "r".  Thus
 
 
        
        
        
14:21 one is the right answer