N = 25

[C1] non-units	[C2] #non-units lead to same #solution for	[C3] #solution for = non-units in C1
0	1	45
5, 10, 20, 15	4	20
	C2TC3 = #ways delta can be non-unit	125

Total non-singular EC over Z₂₅ = 25² - #ways delta can be non-unit (C₂^TC₃) = 500