Step 1: Set up the economy's components.
From the consumption equation \(C = 40 + \beta Y_d\), we know that consumption depends on the personal disposable income \(Y_d\). We are given that \(G = 90\), \(I_A = 80\), \(\beta = 0.75\), and \(\delta = 0.20\). Government tax revenue \(T_x = \delta Y = 0.20Y\).
Step 2: Calculate aggregate output \(Y\).
The equilibrium condition in the economy is:
\[
Y = C + I_A + G
\]
Substituting the consumption function \(C = 40 + 0.75Y_d\) where \(Y_d = Y - T_x\), we get:
\[
C = 40 + 0.75(Y - 0.20Y)
\]
Simplifying:
\[
C = 40 + 0.75(0.80Y) = 40 + 0.60Y
\]
Now, substitute into the equilibrium equation:
\[
Y = 40 + 0.60Y + 80 + 90
\]
Simplifying further:
\[
Y - 0.60Y = 210
\]
\[
0.40Y = 210
\]
\[
Y = 525
\]
Step 3: Calculate tax revenue and surplus.
Tax revenue \(T_x = 0.20Y = 0.20 \times 525 = 105\).
The budget surplus is the difference between government expenditure and tax revenue:
\[
\text{Surplus} = T_x - G = 105 - 90 = 15
\]
Step 4: Conclusion.
The correct answer is (A), with tax revenue of Rs. 105 and a budget surplus of Rs. 15.