Where The Shopkeeper Loses

A currency has coins worth 1, 3 and 4. The shopkeeper's algorithm hands over the largest coin that does not exceed the remaining amount, then repeats. The minimum number of coins needed for each amount is:

amount 1 2 3 4 5 6 7 8 9 10
fewest coins 1 2 1 1 2 2 2 2 3 3

On which of these amounts does the shopkeeper hand over more coins than the minimum?

A

9 and 10

B

6 and 10

C

6 only

D

6, 9 and 10