Need help with this Part

Hey everyone,

I've been trying to figure out how to get the correct mass for this part. I've tried multiple angles and I always end up with the same mass of 1306.29 grams  with 6061 alloy. So I was wondering if any of you would take a crack at it! I attached two pictures with the part plus dimensions, also the second picture contains the answer (question 4) reported in the back of the book.

Thanks everyone!

Edit : THANK YOU TO EVERYONE WHO HELPED

SolidworksParts And Features