!!! I NEED HELP ASAP !!!

Sally wants to save for a new cell phone. She opens a bank account with $40 and adds $20 each week. Which of the following equations can be used to determine how much she has after
'W' weeks?

T = 60w
T = 40 + 20w
T= 20 + 40w
T = 40 + 20 + w