replacing lowest test grade with final if final is higher formula help

Hello all,
I am putting together a gradebook and am having problems coming up with an IF statement to replace the lowest, non zero test grade with the final.

If A1:A4 are the test and A5 is is the final, what would I need to do for the formula to look at the lowest, non zero test of those 4 and if the final is larger, replace it?

Thanks