I need to plot a histogram for the data:
10.478 7.268 2.775 0.381 0.979 1.226 1.392 4.706
0.003 5.004 2.835 2.441 1.838 10.780 0.010 4.732
3.042 8.817 0.670 1.693 11.576 2.469 9.905 2.265
1.184 0.093 5.187 1.828 7.140 0.136 1.408 6.349
3.717 7.170 0.609 3.084 0.122 3.154 3.574 0.420
The data seem to be exponentially distributed. With maximum lokelihood I estimate $\lambda$ to $\lambda = \frac{1}{\bar x} = 0.2808$. Now I have to plot the density function in the same figure as histogram. But i have to scale the density function to let it look well. Here is the histogram with density function multiplied by $\sum_{i=1}^{40} x_i$ and without scaling: 
How do I scale it in the right way? Thanks in advance!