what is the null and alternative hypothesis?

In a sample of 61 business trips taken by employees in the HR department, a company finds that the average amount spent for the trips was $1480 with a standard deviation of $450. In a sample of 101 trips taken by the employees in the sales department is $1650 with a standard deviation of $550. When testing the hypothesis (at the 5% level of significance) that the average amount spent on trips taken by the sales department are higher than those taken by the HR department what is the null and alternative hypotheses?