What would the Null and Alternative Hypotheses be for the following contention?

" What would the Null and Alternative Hypotheses be for the following contention?'It is often felt that the order priority of critical would have higher shipping costs than an order of low priority."

The question relates an assignment whereby a Company has 5 different order priority being Critical, High, Medium, Low and Not Specified. What would be an appropriate Hypothesis Test in this case.