in running a linear regression test for the below, what would be the dependent and independent variables?

A direct marketing company is interested in finding the relationship between age of their customers and the number of orders customers place in a given year. The company randomly samples 25 customers and records their age and computes the total orders they placed last year.The data is in age.sav. Run a simple linear regression to explain the impact of age on number of orders. Express the model you are estimating and state the null and alternate hypothesis.Given the results of your estimation, what is the expected number of orders placed by a 55-year-old customer