Standard Appliances obtains refrigerators for $$1,580$ less $27\%$ and $6\%.$ Standard's overhead is $17\%$ of the selling price of $$1,640.$ A scratched demonstrator unit from their floor display was cleared out for $$1,300.$

a$.$ What is the regular rate of markup on cost for a demonstrator unit?

$\%$

b$.$ What is the rate of markdown on the demonstrator unit?

$\%$

c$.$ What is the operating profit or loss on the demostrator unit?

d$.$ What is the rate of markup on cost that was actually realized for the scratched demonstrator unit?

$\%$