Question
What are the missing numbers?
2113, (a)          , 2133, 2143, (b)          , 2163
2 m
(a)

Click button first when a symbol is required. X

(b)

Click button first when a symbol is required. X

What are the missing numbers?
2113, (a)          , 2133, 2143, (b)          , 2163