Comment by periblepsis on Simplying a digital logic circuit to minimize propagation delay

@IbrahimRabbani 18 pretty much tells you exactly what to use. You are going to use two or more gates with a max of 10 among them, followed by exactly one 8. There's only one 8 to pick. So that's a given. And the NOR2 doesn't look like a good candidate for 10, so perhaps start with the NAND3 using 3 inputs and providing one input to a NAND2 and one other gate with 10 or less that can incorporate the remaining input and provide the other input to the NAND2. This can't be that hard.