$d_{1} = a_{1} + b_{1}$
$e_{1} = a_{1} - b_{1}$
$f_{1} = c_{1} + d_{1}$
$g_{1} = c_{1} - e_{1}$
$a_{2} = f_{1} + g_{1}$
$b_{2} = f_{1} - g_{1}$
$c_{2} = d_{1} + e_{1}$
So, variables used : $a_{1}, a_{2}, b_{1}, b_{2}, c_{1}, c_{2}, d_{1}, e_{1}, f_{1}, g_{1}$
Total 10 variables are required to convert given code into static single assignment form.
