The Relational Algebra expression in the question above, does 4 operations, step by step ( innermost braces first ) .
1. Select those tuples from relation r which satisfies
expression/condition F1, say the result of this
operation is set A.
2. Select those tuples from set A which satisfies
expression/condition F2, say the result of this
operation is set B.
3. Select attrributes set A2 from set B, say the
result of this operation is set C.
4. Select attrributes set A1 from set C, say the
result is set D which is the final result.
Now to optimize this expression, we can combine operations/steps 1 and 2 by AND operator between F1 and F2 condition, like F1 ^ F2, and instead of selecting first attribute set A2, we can directly select attribute set A1 from the result of the combined operation, which is represented by expression in Option A .