3 men = 4 women.

1 man = ⁴/₃ women.

7 man = ²⁸/₃ women.

7 men and 5 women = 5 + (²⁸/₃) = ⁴³/₃ women.

4 women can plough field in 43 days.

So,

1 women can plough in = 43 *4 days.

Hence,

⁴³/₃ women can plough = ^(43*4*3)/₄₃ = 12 days.

According to the question, \begin{align} & \left[ {\frac{{\left( {x - 8} \right)}}{{36}} + \frac{{\left( {x - 12} \right)}}{{54}} + \frac{x}{{72}}} \right] = 1 \cr & \left[ {\frac{{\left( {6x - 48 + 4x - 48 + 3x} \right)}}{{216}}} \right] = 1 \cr & 13x - 96 = 216 \cr & 13x = 216 + 96 = 312 \cr & x = \frac{{312}}{{12}} \cr & \, \, \, \, \, = 24\, {\text{days}} \cr\end{align}

Hence,

Part of cistern filled in X min + part of cistern filled in 3 min = full cistern

[(^7X/_8*12)+(^5X/_6*16)]+[(³/₁₂)+(³/₁₆)] = 1

(^12X/₉₆)+(⁷/₁₆) = 1

Thus,

X = 4.5 min.

Total wage = Rs. 1800

6 * 5x + 4 * 6x + 4 * 9x = 1800. [As A, B, C works for 6, 4, 9 days respectively]

Or, 90x = 1500;

Or, x = ¹⁸⁰⁰/₉₀;

Total amount of A,

= ^1800*30/₉₀ = Rs. 600.

Now, consider option (1).

15 trips and 150 passengers means efficiency of A = 10 passengers per trip.

A's efficiency = 10 passengers per trip.

Then, (B+C) combined efficiency = 50 passengers per trip.

Since, combined efficiency is 60 so option (1) is correct.