A little help will be appreciated!!
Grace loves to download new music. She originally had 47 songs but plans to purchase 3 new songs each week. She wants to know how many songs she will have after 104 weeks. Which equation should she use?

The answer choices are:
A. a104 = 104 + 3(47 − 1)
B. a104 = 104 + 3(47 + 1)
C a104 = 47 + 3(104 − 1)
D. a104 = 47 + 3(104 + 1)