Step 1: Spot the clue in the case:
The sentence is about the size of the money need. Nothing in it speaks of debt, equity or return, so we look for the idea that deals with how much.
Step 2: Recall the related idea:
Think of a family budget made before a wedding. First you add up the expected spending, then you decide where the money will come from. In a firm, the first part of that job is called financial planning.
Step 3: Test option (A).
Financial leverage shows how debt affects shareholders' earnings. The consultant said nothing about earnings here, so we drop this one.
Step 4: Test option (B).
Trading on equity is about gaining when borrowing is cheaper than the return on assets. The line has no hint of this gain, so we drop it.
Step 5: Test option (C).
Capital structure comes into play only after the total need is known, when we split it between debt and equity. The line gives a total, not a split, so this does not fit.
Step 6: Test option (D).
Financial planning covers estimating the total need. The Rs. 50 lakhs figure is such an estimate. This fits the line fully, so we keep it.
Final Answer:
The estimate of Rs. 50 lakhs is a planning step, which matches financial planning, option 4.
\[ \boxed{\text{Option 4}} \]