Consider the expression \((a-1) * (((b+c)/3)+d)\). Let \(X\) be the minimum…

Consider the expression $(a-1) * (((b+c)/3)+d)$. Let $X$ be the minimum number of registers required by an optimal code generation (without any register spill) algorithm for a load/store architecture, in which 

1.  only load and store instructions can have memory operands and 

2.  arithmetic instructions can have only register or immediate operands.

The value of $X$ is _____________ .