27. A program to encrypt pictures has different run times based on the resolution of the picture.
The following table indicates the run times versus megapixels to process a picture.
Run Time (seconds)
4
6
8
Resolution (megapixels)
10 MP
15 MP
20 MP
If the program takes 3 seconds for setup and can run processes in parallel using two proces. sors, how long will the series/parallel solution take if two 10 MP, one 15 MP, and one 20 MP pictures need to be processed, assuming the four processes are not dependent on each other?
(A) 5 seconds
(฿)10 seconds
(C) 15 seconds
(D) 20 seconds

With details please.
Note: This is in the APCSP Barron’s Textbook, their answer key is 20 but that doesn’t make sense even based on the explanation they provided.
I got 15 as an answer