Theoretical Distribution

In a sample of 800 students, the mean weight and standard deviation of weight are found to be $50\mathit{K}\mathit{g}$ and $20\mathit{K}\mathit{g}$ respectively. On the assumption of normality, what is the number of students weighing between $46\mathit{K}\mathit{g}$ and 62 Kg? Given area of the standard normal curve between $\mathit{Z}=0$ to $\mathit{Z}=0.20=0.0793$ and area between $\mathit{Z}=0$ to $\mathit{Z}=0.60=0.2257$.