Explanation:

- Let’s say 1 man's 1 day work = M, and 1 woman's 1 day work = W.

- 50 men + 60 women can do work in 5 days:

(50M + 60W) × 5 = 1 (total work) ? 250M + 300W = 1

- 30 men + 20 women can do it in 9 days:

(30M + 20W) × 9 = 1 ? 270M + 180W = 1

- Solving these:

From first: 5M + 6W = 0.02

From second: 3M + 2W = 0.0111

- Solve for M, W:

Multiply second by 3: 9M + 6W = 0.0333

Subtract first from this: (9M + 6W) - (5M + 6W) = 0.0333 - 0.02 ? 4M = 0.0133 ? M = 0.00333

Plug M into first: 5×0.00333 + 6W = 0.02 ? 0.01665 + 6W = 0.02 ? 6W = 0.00335 ? W = 0.000558

- Work done by 4 men and 6 women daily:

4M + 6W = 4×0.00333 + 6×0.000558 = 0.01332 + 0.003348 = 0.016668

- Days needed = 1 / 0.016668 ˜ 60 days

Correct Answer:

- ?? Option 3: 60 days

- Option 1 (45 days), Option 2 (40 days), Option 4 (36 days): Too short, given the low daily output.

- Option 5 (None of these): Not needed because Option 3 fits.