I have this math problem for homework and i cant get the answers. who can help me plz?

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Math Problem:

Suppose you have, say, a stone tablet of some sort. The tablet (4x4) has 16 pieces missing. But lucky you, you have the pieces! You can tell by looking at the pieces which ones are the four corners, which ones are the eight side pieces, and which ones are the inside pieces. Otherwise, you can't tell where on the tablet they should go or how they should be oriented.

If it takes 90 seconds to place all of the pieces, how many days will it take to try every possible combination? Please round to the nearest full day.

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please, this is a kind of extra credit for my class, and i need the extra credit for the class..

thx for your help!