Smith's Irrigation Supply, Inc., purchases PVC pipe from the manutacturer under credit terms of $\frac{3}{15},n30.$ Assuming it buys $$500$ day, $360$ days per year, answer the following:

a$.$ If Smith's pays on the tenth day, how much is its total discount for the year?

b$.$ Assume instead that Smith's forgoes the early payment discount for the extra financing it receives. What is the effective interest rate $($cost$)$ of the forgone early discount?