Been a long time I haven't revised my lessons. My Insight may be a little poor right now. But the question appears quite easy.
(1) If order matters, for ex. AB, BA counts as two combinations.
10 numbers (1,2,3,4,5,6,7,8,9,0) to be inserted into 2 slots:
26 alphabets (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z) to be inserted into the 5 slots:
Finally, linking the two events together (By Product Principle law):
(2) If order don't matters, then