How would I enter this into the IF formula box in Excel?

Create an IF function in the Discount column to calculate the discount on the criteria below.

1. 50% Discount on the Item Price for any Quantity over 4. Ex. if an Item Price was $5 and if 7 items were purchased, 3 would receive a Discount of $7.50 (3 x 5.00 x 50%).

The Greasy Bean Coffee Company