Color Problem: Compute the Planck function in wavelength for filter centroids B=4400A, V=5500A, R=6200A and I=7700A, for temperatures 3000K, 5000K, 10000K and 20000K. The temperatures correspond roughly to M,G,A,B stars. Using the Planck curves as fluxes (dlambda=1A) is fine. Compute the colors in terms of magnitude: B-V and R-I for each case. Use the Vega system.