Consider the expression (a - b) + e * (c + d). Let X be the minimum number of…

Consider the expression (a - b) + e * (c + d). Let X be the minimum number of registers required by an optimal code generation algorithm for a load/store architecture, in which:

i. Only load and store instructions can have memory operands, and

ii. Arithmetic instructions can have only register or immediate operands.

The value of X is ________.