Which XXX calculates the area using the CalcSquare$()$ function? The formula to calculate the area of a circle is pi $*$ r$^2$

Flowchart Main has no variables and $3$ nodes. Node $1$ is the start node and points to node $2.$ Node $2$ code: Put CalcArea$(5\mathrm{.}0)$ to output Node $2$ points to node $3.$ Node $3$ is the end node. Flowchart CalcArea has $1$ parameter variable $($float r$),1$ local variable $($float PI$\_$VAL$),1$ return variable $($float area$),$ and $4$ nodes. Node $1$ is the start node and points to node $2.$ Node $2$ code: PI$\_$VAL $=3\mathrm{.}14159265$ Node $2$ points to node $3.$ Node $3$ code: XXX Node $3$ points to node $4.$ Node $4$ is the end node. Flowchart CalcSquare has $1$ parameter variable $($float num$),1$ return variable $($float numsq$),$ and $3$ nodes. Node $1$ is the start node and points to node $2.$ Node $2$ code: numsq $=$ num $*$ num Node $2$ points to node $3.$ Node $3$ is the end node.

a$.$

PI$\_$VAL $*$ r $*$ r

b$.$

PI$\_$VAL $*$ CalcSquare$($r$)$

c$.$

area $=$ PI$\_$VAL $*$ CalcSquare$($r$)$

d$.$

area $=$ PI$\_$VAL $*$ CalcSquare$($r$)*$ CalcSquare$($r$)$