D. Although I'm not 100% sure
Can you put more information into this question
Volume of water in the tank:

Differentiate both sides with respect to time <em>t</em> :

<em>V</em> changes at a rate of 2000 cc/min (cubic cm per minute); use this to solve for d<em>h</em>/d<em>t</em> :


(The question asks how the height changes at the exact moment the height is 50 cm, but this info is a red herring because the rate of change is constant.)
$469.
376/4 = 94.
Then add that too 346
94 + 346 = 469