An identifier consists of 2 letters chosen from {m, n, p, r,…
An identifier consists of 2 letters chosen from {m, n, p, r, s} followed by 3 digits from 0–9. (1) How many identifiers are possible if letters and digits may repeat? (2) How many identifiers are possible if letters may repeat but digits may not repeat? (3) How many identifiers containing at least one repeated letter or repeated digit? (Please fill each blank with an integer and without comma or period.)