Nested IF: grade bands in the right order

An IF can have another IF where its false answer goes. That gives you a chain: if this, otherwise if that, otherwise if the other, otherwise the last one.

Chains like this are read top to bottom and stop at the first test that is true. So the order has to run from the hardest band to the easiest. Start with >=60 and every score above sixty is caught by it, the nineties never reach the A test, and every grade comes out the same.

Four bands need three tests. The final answer covers everything left over, so there is nothing to test for it.