The correct answer is 21.
Given: The price for an empty house is either Rs. 10 lakhs if it doesn't have a parking spot or Rs. 12 lakhs if it does.
In Block YY, both E1 and E2 are vacant, and one of them costs 15 lakhs. Let's focus on E1.
For E1:
Neighbor count = 1 (exactly one of D1 or F1 is occupied)
Road adjacency = 0
So, the cost of E1 would be: \((10 \text{ or } 12) + 5 \times 0 + 3 \times 1 = 13 \text{ or } 15\) lakhs.
Since 15 lakhs is the lowest cost for a house in Block YY, E1 must cost 15 lakhs. This implies E1 is the only house in YY with a parking space.
let's calculate the maximum possible price of E2.
E2's base price is 10 lakhs since it cannot have a parking space (only one house in YY, E1, has a parking space). The road adjacency for E2 is 1, and the maximum neighbor count of E2 will be 2 (both D2 and F2 are occupied, and E1 is vacant).
So, E2's price would be: \(10 + 5 \times 1 + 3 \times 2 = 21\) lakhs.
Hence, the maximum possible price for E2 is 21 lakhs.
So, the correct option is (D): 21 lakhs.