Don't understand "Create =IF formula that can be copied"

[daniel1965]

Name Dept. Rate Hours Gross Pay
Sally 1 10 20
Joe 2 10 50
Jill 1 20 44
TOTAL 114 $-

I'm taking an online Excel class and the homework assignment asks me to create an =IF formula for the gross pay column shown above. It's due on Sunday night and the instructor does not answer questions over the weekend. I don't understand what the assignment is asking when it states "Create an =IF formula that can be copied". I'm not asking for you to do the formula for me, I just need to understand what it means to create a formula that can be copied? I've read the chapter and I just can't find this info in the chapter. Thanks for your help.

Assignment Question:
. Write an =IF formula for cell E10 that can be copied and will calculate the gross pay based upon the following information: Dept. 1 employees receive straight time for 40 hours or less and double time for hours over 40. Dept. 2 employees receive straight time for 40 hours or less and triple time for hours over 40.

Dan Johnson
Excel 2010
Windows 7

[martindwilson]

i think it means in this case create a formula that you can fill down in e1 so if you put =$d$1 that would be no good as filling it down would not change nor would =D$1 but =D1 and =$D1 would

[Pepe Le Mokko]

Lucky you ! Usually no help for homework - Martin is in a good mood

[daniel1965]

i think it means in this case create a formula that you can fill down in e1 so if you put =$d$1 that would be no good as filling it down would not change nor would =D$1 but =D1 and =$D1 would

The instructor replied to my question today which is unusual because it's Saturday. He was just asking us to use autofill to recreate the formula for each row which is exactly what you thought Martin. I wasn't using the format $d$1 so I was able to use autofill without changing my formula at all.
Thanks Martin,
Dan Johnson