Help with plotting graph: Plotting multiple lines with equations

I'm struggling to plot this graph.

These are the equations:

and these are the variables:

</matlabcentral/answers/uploaded_files/38549/variables.png> σ = 5.670367 × 10-8 kg s-3 K-4

Can anyone show me the input you would use for matlab?

Thank you in advance for any help you can provide.