We differentiate the expression with respect to t:



We need to find y. We do this by substituting `x = 3.2` into the original expression:


Solving this gives:






The question tells us to take the positive value only. Substituting our known values gives:


`(71.5)(2)(3.2)(12.9)+` `(72.5)(2)(7.836)(dy)/(dt)=0`


This means the velocity in the y-direction is −5195 km/h.