[M.D. Holloway]

You could make a smaller more manageable size replica out of ice and do a simulation and figuer it out.

The dimensions might be tricky though. One thing you could do is make a mold of a smaller version of that car - use a MiniChamps model as your positive for your smaller version and time its melt in the same condisitons then just extrapolate for the larger scale.

That is a pretty big block of ice so the weight of the keys might be pretty in significant untill its a few cm from the ground. A simple experiment could provide data for this as well. In fact, if you had a few different blocks of ice cut to varying thicknesses with keys frozen inside you could time their melt rate and come up with the an equation to predict the thaw. The trick though is the fact the your temp fluctuates so unless the temp is constant it does make predictions tricky. You will never know precisely how warm/cold it will be on a given day or night.

Noah may have the best suggestion. Find the hot babe with no brain and ask her for the number or her number...