Consider a query A "left$-$deep join tree" is shown below. X$1-$X$2$ are intermediate

relations produced in the plans. It is known that R$1-$R$4$ each has $10000$ tuples and takes $1000$ blocks.

X$1-$X$2$ each has $10000$ tuples. Only $4$ blocks of memory are available. All join operators are $($tuple$-$

based$)$ nested loop join. All the plans are fully pipelined. What is the number of data blocks $($number

of I$/$Os$)$ for the left$-$deep plan?

Figure $2$: Left Deep Join