The order of a leaf node in a $B^+$ - tree is the maximum number of (value, data record pointer) pairs it can hold. Given that the block size is $1K\;\text{bytes}$, data record pointer is $7\;\text{bytes}$ long, the value field is $9\;\text{bytes}$ long and a block pointer is $6 \;\text{bytes}$ long, what is the order of the leaf node?
- $63$
- $64$
- $67$
- $68$