Let relation $1(,,)$ and $2(,,)$ have the following properties: $1$ has $20,000$ tuples and $2$ has $45,000$ tuple, $25$ tuples of $1$fit on one block, and $30$ tuples of $2$ fit on one block. Estimate the cost $($in terms of disk I$/$Os$)$ of the following join strategies for $12$: a$.$ Nested$-$loop join