Answer:
The value is 

Step-by-step explanation:
From the question we are told that 
 The horizontal speed is 

 The horizontal distance is 

Generally the time taken by the hot magma in air before landing is mathematically represented as 
 

=> 

=> 

Generally the initial vertical velocity of the magma when it was lunched is 
 

Then the final velocity of the magma when it hits the ground is mathematically represented s 
 

Here the negative sign mean that the direction of the velocity is towards the negative y -axis 
 So 
 

=> 
