(a) There are 70 ways of placing 8 counters in the squares so that each row contains exactly two counters.
(b) There are 495 ways of placing 12 counters in the squares so that each column contains exactly three counters.
You are given the 4 x 4 grid below.
(a) Find the number of ways of placing 8 counters in the squares (at most one counter per square), so that each row contains exactly two counters.
(b) Find the number of ways of placing 12 counters in the squares (at most one counter per square), so that each column contains exactly three counters.
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