I am unsure how to solve this. I have values for all variables for each wavelength in 10 nm increments, 380,390,400....

My thought was to sum each value of $\displaystyle \tau$ at the given wavelength, but that is not correct.

$\displaystyle \tau_{SB} = \frac{\int_{380}^{500}\tau(\lambda) \times W_B(\lambda) d\lambda}{\int_{380}^{500} W_B(\lambda) d\lambda}$

Thanks for any help.