John has exactly 10 coins each of which was minted in 1910 or 1920 or 1930, how many of his coins were minted in 1920 ?

Statement (1) Exactly 6 of his coins were minted in 1910 or 1920.
But how many in 1920?
All 6, 5,4,3... Or nothing. (Insufficient)

Statement (2) Exactly 7 of his coins were minted in 1920 or 1930.
But how many in 1920?
All 7,6,5,.... Or nothing at all.
(Not sufficient)

1&2: let 1910 be A
1920 be B and 1930 be C
A+B=6 ------(1)
B+C=7 ------(2)
A+B+C=10 ----(3)
Equate 1&3
C=4
And from equation 2&3
A=3
Therefore B=3
So 3 coins were minted in 1920

Answer is C
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Hello one prompt question, regarding this question , statement A says, "Exactly 6 of his coins were minted in 1910 or 1920", so in the beginning I thought that all 6 of them were either minted in 1910 or 1920 , only by combining both statements I realized that eg.3 could have been made in 1910 and the other 3 in 1920 etc. , so I was wondering, how would the wording be if we meant that all 6 of them were minted in a single year 1910 or 1920?