You and your team are tasked with sorting a hundred metallic samples composed of pure silver (Ag), nickel (Ni), indium (In), or cobalt (Co). The problem is the they all look the same (metallic) and are not labeled. The work functions (wo) of the materials are: Ag (4.55 eV), Ni (5.17eV), In (4.13 eV), and Co (4.87 eV). You have a monochromatic light source that can be tuned to output wavelengths from 250 nm to 400 nm. You get the idea to use it to measure the threshold frequencies of the samples and, therefore, to identify the metals. 

(a) Calculate the threshold frequencies and wavelengths of all of the metals. 

(b) Can the light source reach the threshold frequencies of all the metals? If not, can it still be used to sour the samples?