(d) $\theta_{mix} = \frac{m_{W}\theta_{W} - \frac{m_{i}L_{i}}{S_{W}}}{m_{i} + m_{W}} = \frac{300 \times 25 - \frac{100 \times 80}{1}}{100 + 300} = - 1.25℃$ Which is not possible. Hence $\theta_{mix} = 0℃$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.